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Crystals
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Feature Papers in Crystals 2023
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Feature Papers in Crystals 2023

A special issue of Crystals (ISSN 2073-4352).

Deadline for manuscript submissions: closed (31 December 2023) | Viewed by 25132

Special Issue Editors

Prof. Dr. Helmut Cölfen
*
Website
Guest Editor
Physical Chemistry, Universität Konstanz, 78457 Konstanz, Germany
Interests: nucleation; nanoparticle self organization; non classical crystallization; mesocrystals; biomineralization; nanoparticle analysis by fractionating methods
* We dedicate the memory of the editor Professor Dr. Helmut Cölfen who passed away during this special issue period.
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Shujun Zhang

grade E-Mail Website
Guest Editor
ISEM/AIIM, University of Wollongong, Wollongong, NSW 2500, Australia
Interests: piezoelectricity; ferroelectricity; crystals; ceramics; transducers
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Jesús Sanmartín-Matalobos

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Guest Editor
Inorganic Chemistry Department, University of Santiago de Compostela, 15782 Santiago de Compostela, Spain
Interests: supramolecular chemistry; coordination chemistry; single crystal X-ray crystallography; H-bonding; chirality; fluorescence
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Heike Lorenz

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Guest Editor
Max Planck Institute for Dynamics of Complex Technical Systems, 39106 Magdeburg, Germany
Interests: phase equilibria; crystallization kinetics; process monitoring & design; separation of fine chemicals, large scale industrial products and renewable resources; innovative crystallization-based separation concepts; enantiomers; natural products; multi-component mixtures
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Sławomir Grabowski

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Guest Editor
Kimika Fakultatea, Euskal Herriko Unibertsitatea UPV/EHU, Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Spain
Interests: hydrogen bond; lewis acid–Lewis base interactions; atoms in molecules theory; ab initio calculations
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Crystals are a very important class of structured materials both from a scientific and technological viewpoint. They have not only fascinated humankind from the beginning, but are also essential for our modern life. Therefore, crystal science and technology is a very wide field with a significant impact on numerous areas. This is the topic that the journal Crystals has focused on. To mark important developments in the science of crystals, we are launching a Special Issue edited by the Editor in Chief and Section Editors in Chief and wish to invite all Editorial Board Members as well as prominent scientists in the field to contribute in the form of feature papers covering a special topic of crystallization science. The coverage of topics of this Special Issue is as broad as that of the journal, ranging from nucleation, growth, processing, and characterization of crystalline and liquid crystalline materials to the mechanical, chemical, electronic, magnetic, and optical properties of crystals, as well as the diverse applications of (nano)crystalline materials. In addition, all modern methods for the characterization of crystal nucleation and growth are of interest, including high-resolution characterization techniques such as synchrotron radiation or X-ray free electron laser-based techniques. We would like to reflect the broad field of crystalline materials in this Special Issue, and contributions in the field of all the above-mentioned topics are welcome, as well as those from common applications.

We very much look forward to your valued contributions to make this Special Issue a unique resource for future researchers from the exciting field of crystals.

Prof. Dr. Helmut Cölfen
Prof. Dr. Shujun Zhang
Prof. Dr. Jesús Sanmartín-Matalobos
Prof. Dr. Heike Lorenz
Prof. Dr. Slawomir Grabowski
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • crystals
  • crystal growth
  • characterization techniques
  • crystalline structure
  • properties and applications of crystalline materials

Published Papers (27 papers)

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17 pages, 2776 KiB  
Article
Homogeneous Organic Crystal Nucleation Rates in Solution from the Perspective of Chemical Reaction Kinetics
by Sven L. M. Schroeder
Crystals 2024, 14(4), 349; https://doi.org/10.3390/cryst14040349 - 06 Apr 2024
Viewed by 507
Abstract
It is demonstrated for 11 different combinations of organic solutes and solvents that the supersaturation dependence of homogeneous organic crystal nucleation rates from solution can be predicted from the solubility, bar a single empirical rate constant, when it is assumed that nucleation takes [...] Read more.
It is demonstrated for 11 different combinations of organic solutes and solvents that the supersaturation dependence of homogeneous organic crystal nucleation rates from solution can be predicted from the solubility, bar a single empirical rate constant, when it is assumed that nucleation takes place in reversible aggregates of solvated solutes formed in supersaturated solutions. Reversible solute aggregation represents natural solute density fluctuations that take place in any solute/solvent system. For thermodynamically ideal solutions, the steady state size distribution, and thus the population of reversible aggregates in supersaturated solution, can be predicted quantitatively from the overall solute concentration by a simple mathematical expression. Supersaturation creates an excess of reversible aggregates with sizes exceeding that of the largest aggregate in saturated solution. It is shown that the number of these excess aggregates is proportional to experimental homogeneous nucleation rates, suggesting a rate equation for homogeneous nucleation that has only one empirical parameter, namely, a rate constant specific to the solute/solvent combination. This rate constant can be determined from standard nucleation rate data. The system-specificity of homogeneous nucleation rates thus appears to be encoded solely in a rate constant for the transformation of the large excess aggregates into crystal nuclei. The driving force for triggering nucleation events in these aggregates is likely the extremely high local supersaturation, which provides the conditions for spatiotemporally aligned bond-breaking (e.g., de-solvation) and bond-forming (e.g., solute–solute bonding) events that create stable crystal nuclei. The possible influence of heterogeneous nucleation by solid impurities is considered. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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9 pages, 1475 KiB  
Article
Variable-Temperature Non-Linear Optical Imaging Witnesses Change in Crystalline Rotor Dynamics at Phase Transition
by Guillaume Bastien, Cécile Mézière, Patrick Batail and Denis Gindre
Crystals 2024, 14(3), 259; https://doi.org/10.3390/cryst14030259 - 06 Mar 2024
Viewed by 779
Abstract
We present a novel approach to second harmonic microscopy combining variable temperature and photon counting. This innovative method aims to generate Second Harmonic Generation (SHG) images by scanning the same area multiple times with short pixel dwell times and low excitation intensities, as [...] Read more.
We present a novel approach to second harmonic microscopy combining variable temperature and photon counting. This innovative method aims to generate Second Harmonic Generation (SHG) images by scanning the same area multiple times with short pixel dwell times and low excitation intensities, as illustrated by imaging the full extent of a single crystalline rod of (1,4-bis((4′-(iodoethynyl)phenyl) ethynyl) bicyclo[2.2.2]octane (BCO). Remarkably, this new technique records the change in SHG intensity that occurs along with the crystalline phase transition at 108 K, thereby showing great promise in exploring the intricate instabilities of rotator dynamics concealed within the phase diagrams of molecular machines. Notably, our findings reveal a sustained decrease in non-linear optical intensity as the temperature drops to 95 K, followed by a sharp increase in SHG intensity at approximately 108 K, in synchronicity with the phase transition reported earlier that involves an intricate set of concerted changes in rotor dynamics. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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9 pages, 6754 KiB  
Article
Dielectric Terahertz Characterization of Microwave Substrates and Dry Resist
by Silvia Tofani, Tiziana Ritacco, Luca Maiolo, Francesco Maita, Romeo Beccherelli, Walter Fuscaldo and Dimitrios C. Zografopoulos
Crystals 2024, 14(3), 205; https://doi.org/10.3390/cryst14030205 - 21 Feb 2024
Viewed by 742
Abstract
Microwave fabrication and design techniques are commonly employed in the terahertz (THz) domain. However, a characterization of commercially available microwave dielectric materials is usually lacking at sub-THz and THz frequencies. In this work, we characterized four substrates by Rogers and an Ordyl dry [...] Read more.
Microwave fabrication and design techniques are commonly employed in the terahertz (THz) domain. However, a characterization of commercially available microwave dielectric materials is usually lacking at sub-THz and THz frequencies. In this work, we characterized four substrates by Rogers and an Ordyl dry resist between 0.2 and 2 THz, in terms of relative permittivity and loss tangent. The reflectance spectra of the investigated materials were retrieved by means of THz time-domain spectroscopy in reflection mode and post-processed according to a transmission-line model in which the materials’ parameters are fit by means of the Havriliak–Negami variation of the Debye model. The relative permittivity of the investigated materials showed negligible frequency dispersion in the sub-THz and in the THz range. In terms of the loss tangent, the Rogers substrates revealed a more pronounced frequency-dispersive behavior among different materials, as dictated by the Havriliak–Negami model. The Ordyl resist was dispersive in the 0.2–1.2 THz range and presented a nearly constant loss tangent value between 1.2 and 2 THz. These results may represent a reference for the development of innovative components for THz and sub-THz emerging applications. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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14 pages, 4544 KiB  
Article
The Crystal Structure and Physicochemical Properties of New Complexes Containing a CuII-LnIII-CuII Core
by Beata Cristóvão, Dariusz Osypiuk and Barbara Mirosław
Crystals 2024, 14(2), 189; https://doi.org/10.3390/cryst14020189 - 14 Feb 2024
Viewed by 768
Abstract
Three new cationic complexes, [Cu4Tb2(H2L)4(NO3)4(H2O)3](NO3)2·5.5H2O·2MeOH (1), [Cu4Ho2(H2L)4(NO3)4(H [...] Read more.
Three new cationic complexes, [Cu4Tb2(H2L)4(NO3)4(H2O)3](NO3)2·5.5H2O·2MeOH (1), [Cu4Ho2(H2L)4(NO3)4(H2O)3](NO3)2·7.5H2O (2), and [Cu4Er2(H2 L)4(NO3)4(H2O)3](NO3)2·7H2O·3MeOH (3), were synthesized and studied using elemental and TG/DTG/DSC analyses, single-crystal X-ray diffraction, and magnetic measurements. The structure analysis showed that 1–3 crystallize as (NO3)-bridged compounds and that the lanthanide(III) ion acts as a joint connecting two [CuH2L] coordination units. In each heterotrinuclear unit, an asymmetry in the degree of planarity of the bridging CuO2Ln fragments is observed. The CuII ions are five- and six-coordinate, with distorted square pyramidal and octahedral geometry, respectively, whereas the LnIII ions are nine-coordinate. The solvates 1–3 are stable at room temperature, and their desolvation process is consistent with the loss of water and/or methanol molecules. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicate the weak ferromagnetic interaction between the paramagnetic centers CuII and TbIII/HoIII 1 and 2. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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13 pages, 3731 KiB  
Article
Crystal Structure of New Zinc-Hydroxy-Sulfate-Hydrate Zn4(OH)6SO4·2–2.25H2O
by Tsveta Stanimirova, Rositsa Nikolova and Nadia Petrova
Crystals 2024, 14(2), 183; https://doi.org/10.3390/cryst14020183 - 12 Feb 2024
Viewed by 867
Abstract
A theoretical model of the crystal structure of the newly obtained compound Zn4(OH)6SO4·2–2.25H2O based on the compilation of the crystal–chemical properties of two known zinc-hydroxy-sulfate phases—mineral namuwite and hemihydrate—is proposed. The single XRD data confirmed [...] Read more.
A theoretical model of the crystal structure of the newly obtained compound Zn4(OH)6SO4·2–2.25H2O based on the compilation of the crystal–chemical properties of two known zinc-hydroxy-sulfate phases—mineral namuwite and hemihydrate—is proposed. The single XRD data confirmed the model and determined the structure, with a trigonal symmetry SG of P-3, the unit cell with a = 8.3418(15) Å and c = 17.595(7) Å, and a cell volume of 1060.3(6) Å3, with Z = 2. The results show that the Zn4(OH)6SO4·2–2.5H2O crystal structure consists of an alternating paired octahedral–tetrahedral doubly decorated hydroxide layer with cationic vacancies and an aqueous interlayer. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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12 pages, 3721 KiB  
Article
Combining a Drug and a Nutraceutical: A New Cocrystal of Praziquantel and Curcumin
by Camila Caro Garrido, Marie Vandooren, Koen Robeyns, Damien P. Debecker, Patricia Luis and Tom Leyssens
Crystals 2024, 14(2), 181; https://doi.org/10.3390/cryst14020181 - 11 Feb 2024
Viewed by 1064
Abstract
This study explores the co-crystallization between the drug praziquantel (PZQ) and the nutraceutical curcumin (CU). The investigation revealed two novel solid forms: a cocrystal solvate with ethyl acetate and a non-solvated cocrystal. This novel drug–nutraceutical cocrystal is a praziquantel–curcumin (2:1) cocrystal. The cocrystal [...] Read more.
This study explores the co-crystallization between the drug praziquantel (PZQ) and the nutraceutical curcumin (CU). The investigation revealed two novel solid forms: a cocrystal solvate with ethyl acetate and a non-solvated cocrystal. This novel drug–nutraceutical cocrystal is a praziquantel–curcumin (2:1) cocrystal. The cocrystal solvate has ethyl acetate molecules occupying the voids with minimal interactions within the crystal lattice. The application of heat treatment induces solvent removal and prompts the transition to the non-solvated cocrystal, as highlighted by variable-temperature X-ray powder diffraction (VT-XRPD). Thermal analyses demonstrate the stability of the cocrystal solvate up to approximately 100 °C, beyond which it transforms into the non-solvated phase, which eventually melts at 130 °C. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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16 pages, 14693 KiB  
Article
FDIP—A Fast Diffraction Image Processing Library for X-ray Crystallography Experiments
by Yaroslav Gevorkov, Marina Galchenkova, Valerio Mariani, Anton Barty, Thomas A. White, Henry N. Chapman and Oleksandr Yefanov
Crystals 2024, 14(2), 164; https://doi.org/10.3390/cryst14020164 - 05 Feb 2024
Viewed by 834
Abstract
Serial crystallography (SX) is a cutting-edge technique in structural biology, involving the systematic collection of X-ray diffraction data from numerous randomly oriented microcrystals. To extract comprehensive three-dimensional information about the studied system, SX utilises thousands of measured diffraction patterns. As such, SX takes [...] Read more.
Serial crystallography (SX) is a cutting-edge technique in structural biology, involving the systematic collection of X-ray diffraction data from numerous randomly oriented microcrystals. To extract comprehensive three-dimensional information about the studied system, SX utilises thousands of measured diffraction patterns. As such, SX takes advantages of the properties of modern X-ray sources, including Free Electron Lasers (FELs) and third and fourth generation synchrotrons, as well as contemporary high-repetition-rate detectors. Efficient analysis of the extensive datasets generated during SX experiments demands fast and effective algorithms. The FDIP library offers meticulously optimised functions tailored for preprocessing data obtained in SX experiments. This encompasses tasks such as background subtraction, identification and masking of parasitic streaks, elimination of unwanted powder diffraction (e.g., from ice or salt crystals), and pinpointing useful Bragg peaks in each diffraction pattern. The library is equipped with a user-friendly graphical interface for facile parameter adjustment tailored to specific datasets. Compatible with popular SX processing software like OnDA, Cheetah, CrystFEL, and Merge3D, the FDIP library enhances the capabilities of these tools for streamlined and precise serial crystallography analyses. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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0 pages, 8339 KiB  
Article
Synthesis of New Zinc and Copper Coordination Polymers Derived from Bis (Triazole) Ligands
by Maria Cristina Al-Matarneh, Alina Nicolescu, Ioan-Andrei Dascalu, Sergiu Shova, Cristian-Dragos Varganici, Adrian Fifere, Ramona Danac and Ioana-Cristina Marinas
Crystals 2024, 14(2), 144; https://doi.org/10.3390/cryst14020144 - 30 Jan 2024
Viewed by 654
Abstract
Recent research has focused on molecules with different aromatic nitrogen-containing moieties coupled to a biphenyl core, as an effective approach for the assembly of coordination polymers. This study presents the synthesis and characterization of new ligands based on 1,1′-(3,3′-dimethoxy-[1,1′-biphenyl]-4,4′-diyl)bis(4-butyl-1H-1,2,3-triazole) (L1) and [...] Read more.
Recent research has focused on molecules with different aromatic nitrogen-containing moieties coupled to a biphenyl core, as an effective approach for the assembly of coordination polymers. This study presents the synthesis and characterization of new ligands based on 1,1′-(3,3′-dimethoxy-[1,1′-biphenyl]-4,4′-diyl)bis(4-butyl-1H-1,2,3-triazole) (L1) and 1,1′-(3,3′-dimethoxy-[1,1′-biphenyl]-4,4′-diyl)bis(4-phenyl-1H-1,2,3-triazole) (L2) and their coordination polymers with Cu(II) and Zn(II). An unexpected coordination polymer with Cu(I) starting from Cu(II) was obtained in the case of the L2 ligand. The ligands and metal complexes underwent thorough characterization, including X-ray diffraction, NMR-, FTIR-, MS-spectrometry, and EPR, XPS, and TG-DTG analyses. While the ligand L2 generated a linear Cu(I) polymer, the ligand L1 formed a zigzag polymer with both copper and zinc. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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22 pages, 8785 KiB  
Article
Insights in the Structural Hierarchy of Statically Crystallized Palm Oil
by Fien De Witte, Ivana A. Penagos, Kato Rondou, Kim Moens, Benny Lewille, Daylan A. Tzompa-Sosa, Davy Van de Walle, Filip Van Bockstaele, Andre G. Skirtach and Koen Dewettinck
Crystals 2024, 14(2), 142; https://doi.org/10.3390/cryst14020142 - 30 Jan 2024
Viewed by 765
Abstract
Palm oil (PO) is still widely used for the production of all types of food products. Due to its triacylglycerol (TG) composition, PO is semisolid at ambient temperature, offering possibilities for many applications. In order to tailor the fat crystal network for certain [...] Read more.
Palm oil (PO) is still widely used for the production of all types of food products. Due to its triacylglycerol (TG) composition, PO is semisolid at ambient temperature, offering possibilities for many applications. In order to tailor the fat crystal network for certain applications, it remains imperative to understand the structural build-up of the fat crystal network at the full-length scale and to understand the effect of processing conditions. In this study, PO was crystallized under four temperature protocols (fast (FC) or slow (SC) cooling to 20 °C or 25 °C) and was followed for one hour of isothermal time. A broad toolbox was used to fundamentally unravel the structural build-up of the fat crystal network at different length scales. Wide-angle and small-angle X-ray scattering (WAXS and SAXS) showed transitions from α-2L to β’-2L over time. Despite the presence of the same polymorphic form (β’), chain length structure (2L), and domain size, ultra-small-angle X-ray scattering (USAXS) showed clear differences in the mesoscale. For all samples, the lamellar organization was confirmed. Both cooling speed and isothermal temperature were found to affect the size of the crystal nanoplatelets (CNPs), where the highest cooling speed and lowest isothermal temperature (FC and 20 °C) created the smallest CNPs. The microstructure was visualized with polarized light microscopy (PLM) and cryo-scanning electron microscopy (cryo-SEM), showing clear differences in crystallite size, clustering, and network morphology. Raman spectroscopy was applied to confirm differences in triglyceride distribution in the fat crystal network. This study shows that both cooling rate and isothermal temperature affect the fat crystal network formed, especially at the meso- and microscale. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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16 pages, 2497 KiB  
Article
Halogen Bonding versus Nucleophilic Substitution in the Co-Crystallization of Halomethanes and Amines
by Olivia Grounds, Matthias Zeller and Sergiy V. Rosokha
Crystals 2024, 14(2), 124; https://doi.org/10.3390/cryst14020124 - 26 Jan 2024
Viewed by 868
Abstract
Haloalkanes and amines are common halogen-bond (XB) donors and acceptors as well as typical reagents in nucleophilic substitution reactions. Thus, crystal engineering using these molecules requires an understanding of the interchange between these processes. Indeed, we previously reported that the interaction of quinuclidine [...] Read more.
Haloalkanes and amines are common halogen-bond (XB) donors and acceptors as well as typical reagents in nucleophilic substitution reactions. Thus, crystal engineering using these molecules requires an understanding of the interchange between these processes. Indeed, we previously reported that the interaction of quinuclidine (QN) with CHI3 in acetonitrile yielded co-crystals showing a XB network of these two constituents. In the current work, the interactions of QN with C2H5I or 1,4-diazabicyclo[2.2.2]octane (DABCO) with CH2I2 led to nucleophilic substitution producing I− anions and quaternary ammonium (QN-CH2CH3 or DABCO-CH2I+) cations. Moreover, the reaction of QN with CHI3 in dichloromethane afforded co-crystals containing XB networks of CHI3 with either Cl− or I− anions and QN-CH2Cl+ counter-ions. A similar reaction in acetone produced XB networks comprising CHI3, I− and QN-CH2COCH3+. These distinctions were rationalized through a computational analysis of XB complexes and the transition-state energies for the nucleophilic substitution. It indicated that the outcome of the reactions was determined mostly by the relative energies of the products. The co-crystals obtained in this work showed bonding between the cationic (DABCO-CH2I+, QN-CH2Cl+) or neutral (CHI3) XB donors and the anionic (I−, Cl−) or neutral (CHI3) acceptors. Their analysis showed comparable electron and energy densities at the XB bond critical points and similar XB energies regardless of the charges of the interacting species. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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11 pages, 5650 KiB  
Article
Anion Doping of Tungsten Oxide with Nitrogen: Reactive Magnetron Synthesis, Crystal Structure, Valence Composition, and Optical Properties
by Insaf F. Malikov, Nikolay M. Lyadov, Myakzyum K. Salakhov and Lenar R. Tagirov
Crystals 2024, 14(2), 109; https://doi.org/10.3390/cryst14020109 - 23 Jan 2024
Viewed by 642
Abstract
Anion doping of tungsten trioxide by nitrogen is used to obtain electrochrome cathode materials, the spectral transmittance of which can be controlled by the doping level. A series of samples was synthesized by reactive magnetron sputtering of a metal tungsten target in a [...] Read more.
Anion doping of tungsten trioxide by nitrogen is used to obtain electrochrome cathode materials, the spectral transmittance of which can be controlled by the doping level. A series of samples was synthesized by reactive magnetron sputtering of a metal tungsten target in a mixture of argon, nitrogen, and oxygen gases, the flow rate of the latter was varied at a constant pressure of the gas mixture. Warm-colored tungsten oxynitride films were prepared at higher doping levels with their morphology and elemental composition characterized using scanning electron microscopy, crystal structure described using X-ray diffraction and the valence state of constituents revealed with X-ray photoelectron spectroscopy techniques. Optical properties were measured by making use of transmission spectrophotometry and spectroscopic ellipsometry. These extensive experimental studies revealed an increase in absorption towards shorter wavelengths below the wavelength of 0.5 µm with an increase in the doping level. At the same time, it was found that with an increase in the doping level, partial reduction of the tungsten occurs, and the fraction of non-stoichiometric oxygen steadily increases to half of the total oxygen content. It is a common belief that the imperfection of the doped material facilitates the intercalation of the material by electrolyte ions. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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12 pages, 3707 KiB  
Article
Phase Formation in NaH2PO4–VOSO4–NaF–H2O System and Rapid Synthesis of Na3V2O2x(PO4)2F3-2x
by Zhi Lin
Crystals 2024, 14(1), 43; https://doi.org/10.3390/cryst14010043 - 28 Dec 2023
Viewed by 833
Abstract
Renewable electricity products, for example, from wind and photovoltaic energy, need large-scale and economic energy storage systems to guarantee the requirements of our daily lives. Sodium-ion batteries are considered more economical than lithium-ion batteries in this area. Na3V2(PO4 [...] Read more.
Renewable electricity products, for example, from wind and photovoltaic energy, need large-scale and economic energy storage systems to guarantee the requirements of our daily lives. Sodium-ion batteries are considered more economical than lithium-ion batteries in this area. Na3V2(PO4)2F3, NaVPO4F, and Na3(VO)2(PO4)2F are one type of material that may be used for Na-ion batteries. In order to better understand the synthesis of these materials, the phase formation in a NaH2PO4–VOSO4–NaF–H2O system under hydrothermal conditions was studied and is reported herein. This research focused on the influences of the sodium fluoride content and hydrothermal crystallization time on phase formation and phase purity. The phase transformation between Na(VO)2(PO4)2(H2O)4 and Na3V2O2x(PO4)2F3-2x was also studied. Na3V2O2x(PO4)2F3-2x with a high degree of crystallinity can be obtained in as short as 2 h via hydrothermal synthesis using a conventional oven at 170 °C without agitation. All compounds obtained in this research were studied mainly using powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrometry, and Fourier-transform infrared spectroscopy. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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13 pages, 9335 KiB  
Article
Optimizing Hot-Work Tool Steel Microstructure for Enhanced Toughness
by Anže Bajželj, Tilen Balaško, Barbara Šetina Batič and Jaka Burja
Crystals 2024, 14(1), 26; https://doi.org/10.3390/cryst14010026 - 26 Dec 2023
Viewed by 856
Abstract
Hot-work tool steels play a crucial role in applications exposed to extreme thermal, mechanical, and chemical stresses and require exceptional properties such as high strength, hardness, wear resistance, and toughness. The latter is crucial to prevent an unexpected tool failure due to the [...] Read more.
Hot-work tool steels play a crucial role in applications exposed to extreme thermal, mechanical, and chemical stresses and require exceptional properties such as high strength, hardness, wear resistance, and toughness. The latter is crucial to prevent an unexpected tool failure due to the formation and propagation of fatigue cracks in demanding environments. In addition, high thermal conductivity is crucial to prevent overheating of the tool and the resulting degradation of the material. This study focuses on a new generation hot-work tool steel with increased Mo and W contents, which has excellent thermal conductivity but limited toughness, as it contains stable Mo-W carbides that remain stable up to 1100 °C. To improve toughness, an alternative heat-treatment method involving austempering at different temperatures was applied. The investigation begins with the characterisation of the chemical composition of the steel, followed by the determination of the martensite-start (MS) and martensite-finish (Mf) temperatures. Based on the results, the researchers established a set of samples for austempering heat treatment. They investigated the effects of different isothermal holding temperatures on the microstructure of the steel and its subsequent mechanical properties. The results show that reduced bainite formation, achieved by austempering at certain temperatures, led to significantly improved impact toughness and moderate hardness. This study also showed a correlation between the isothermal holding temperature and the extent of martensitic transformation, which affected the microstructure and mechanical properties of the steel. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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14 pages, 12242 KiB  
Article
Optical Photon Propagation Characteristics and Thickness Optimization of LaCl3:Ce and LaBr3:Ce Crystal Scintillators for Nuclear Medicine Imaging
by Stavros Tseremoglou, Christos Michail, Ioannis Valais, Konstantinos Ninos, Athanasios Bakas, Ioannis Kandarakis, George Fountos and Nektarios Kalyvas
Crystals 2024, 14(1), 24; https://doi.org/10.3390/cryst14010024 - 26 Dec 2023
Cited by 1 | Viewed by 1226
Abstract
The present study focuses on the determination of the optimal crystal thickness of LaCl3:Ce and LaBr3:Ce crystal scintillators for Nuclear Medicine Imaging applications. A theoretical model was applied for the estimation of the optical efficiency of the two single-crystal [...] Read more.
The present study focuses on the determination of the optimal crystal thickness of LaCl3:Ce and LaBr3:Ce crystal scintillators for Nuclear Medicine Imaging applications. A theoretical model was applied for the estimation of the optical efficiency of the two single-crystal scintillators in terms of Detector Optical Gain (DOG). The theoretical model was validated against the experimental values of the Absolute Efficiency (AE) of the two crystals, obtained in the energy range 110 kVp–140 kVp. By fitting the theoretical model to these experimental data, the propagation probability per elementary thickness k was determined and DOG was theoretically calculated for crystal thicknesses from 0.005 cm to 2 cm, in the energy range of Nuclear Medicine Imaging. k values for LaCl3:Ce and LaBr3:Ce crystals were significantly higher compared to other single-crystal scintillators. The DOG values of the two crystals may serve as evidence that the LaBr3:Ce crystal exhibits significantly better performance compared to the LaCl3:Ce crystal. With an increase in energy, the optimum thickness increases for both crystals. Additionally, crystal efficiency generally demonstrates a decrease beyond a certain thickness. The aforementioned insights may provide valuable guidance for the design and optimization of crystal scintillators in Nuclear Medicine Imaging systems. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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12 pages, 6790 KiB  
Article
Synthesis and Crystallization of N-Rich Triazole Compounds
by Emmanuele Parisi and Roberto Centore
Crystals 2023, 13(12), 1651; https://doi.org/10.3390/cryst13121651 - 30 Nov 2023
Viewed by 922
Abstract
Among N-rich heterocycle backbone compounds, the triazoles building block received a lot of interest in several different academic and industrial studies and applications. This article outlines the process of synthesizing three different 1,2,4-triazole-based systems, commencing with 1,3-diaminoguanidine hydrochloride monohydrate as the starting material. [...] Read more.
Among N-rich heterocycle backbone compounds, the triazoles building block received a lot of interest in several different academic and industrial studies and applications. This article outlines the process of synthesizing three different 1,2,4-triazole-based systems, commencing with 1,3-diaminoguanidine hydrochloride monohydrate as the starting material. The five novel crystal structures, Triaz1, Triaz2, Triaz3, Triaz4, and Triaz5, were characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Hirshfeld surface analysis was employed to explore the intermolecular interactions that are responsible for quantitative crystal packing. The synthesized compounds, with their elevated nitrogen content, serve as potential components for High-Energy-Density material science applications. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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14 pages, 3988 KiB  
Article
Solid Phase and Stability Investigation of a Co-Crystal in the l-Valine/l-Leucine System
by Vico Tenberg, Matthias Stein and Heike Lorenz
Crystals 2023, 13(11), 1542; https://doi.org/10.3390/cryst13111542 - 27 Oct 2023
Viewed by 806
Abstract
Some amino acid systems are known to exhibit solid solution and/or co-crystal behavior upon crystallization, which significantly affects their phase diagrams and complicates the design of their purification processes. Such behaviors are observed in the l-valine/l-leucine system. In this work, [...] Read more.
Some amino acid systems are known to exhibit solid solution and/or co-crystal behavior upon crystallization, which significantly affects their phase diagrams and complicates the design of their purification processes. Such behaviors are observed in the l-valine/l-leucine system. In this work, the formation and stability of a 3:1 co-crystal of the two amino acids (designated as V3L) is further investigated. To accomplish the formation, liquid-assisted grinding, slurry equilibration, and sublimation experiments were performed and analyzed via HPLC and PXRD. Additionally, periodic DFT calculations were used to calculate lattice energies and determine the thermodynamics of possible solid phases. Experimental results show a clear metastability of the investigated V3L co-crystals when compared to its stable solid solution. The calculations underline the metastability and the possible formation of continuous solid solutions between l-valine and l-leucine since lattice energy differences between pure amino acids and mixed compositions are negligible. This previously unknown phase behavior can be used to assess the influence of V3L on the amino acid purification process and provides a basis for investigating similar systems with small energy differences between pure and mixed compositions in future studies. In addition, it demonstrates the particular variability of solid phases and their relationships in such simple but biologically important amino acid systems. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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8 pages, 2384 KiB  
Communication
Formation of an Unusual Pseudo-Square Planar-Induced Mercury(II) Dimeric Complex
by Huiyeong Ju, Dong Hee Lee, Seulgi Kim, Joon Rae Kim, Yunji Kang, Eunji Lee and In-Hyeok Park
Crystals 2023, 13(10), 1475; https://doi.org/10.3390/cryst13101475 - 10 Oct 2023
Viewed by 649
Abstract
Due to the different crystallization methods, two Hg(II) complexes of a 19-membered NO2S2-macrocycle (L) and its oxidized ligand (HLox), exhibiting different stoichiometries, were prepared. First, mercury(II) iodide reacts with L to afford a dinuclear [...] Read more.
Due to the different crystallization methods, two Hg(II) complexes of a 19-membered NO2S2-macrocycle (L) and its oxidized ligand (HLox), exhibiting different stoichiometries, were prepared. First, mercury(II) iodide reacts with L to afford a dinuclear metallacycle complex [Hg2(L)2I4] (1) in which the mercury(II) exists outside the macrocyclic cavity. Meanwhile, the slow diffusion reaction gave an unusual pseudo-square planar-induced mercury(II) complex, which shows three separated parts with the formula [Hg2(HLox)I5]2[HgI2] (2). There are two complex cation units that are exo-coordinated, along with one unit consisting of a metal cluster anion. Surprisingly, L was oxidized in the disulfoxidized form (HLox) in this condition. NMR titration was used to monitor both the structural and binding characteristics of the complex formed between L and mercury(II) iodide in a solution. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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22 pages, 29452 KiB  
Article
Relationships between Strength, Ductility and Fracture Toughness in a 0.33C Steel after Quenching and Partitioning (Q&P) Treatment
by Evgeniy Tkachev, Sergey Borisov, Yuliya Borisova, Tatiana Kniaziuk and Rustam Kaibyshev
Crystals 2023, 13(10), 1431; https://doi.org/10.3390/cryst13101431 - 26 Sep 2023
Cited by 2 | Viewed by 924
Abstract
The effect of quenching and partitioning (Q&P) processing on strength, ductility and fracture toughness is considered in a 0.33% C-1.8% Si-1.44 Mn-0.58% Cr steel. The steel was fully austenitized at 900 °C and quenched to 210 °C for 30 s. Partitioning at 350 [...] Read more.
The effect of quenching and partitioning (Q&P) processing on strength, ductility and fracture toughness is considered in a 0.33% C-1.8% Si-1.44 Mn-0.58% Cr steel. The steel was fully austenitized at 900 °C and quenched to 210 °C for 30 s. Partitioning at 350 °C for 600 s produces a martensitic matrix with transition carbides, bainitic ferrite and film-like retained austenite (RA) that is stable against transformation to strain-induced martensite under tension. This processing provided the highest strength and fracture toughness but the lowest ductility and product of strength and elongation (PSE), σB·δ (MPa·%). Partitioning at 500 °C produced RA with a relatively low carbon content and low volume fraction of carbides. The steel after this Q&P processing exhibits the highest ductility and PSE but low YS and Charpy V-notch (CVN) impact toughness. High ductility and PSE correlate with the ability of RA to transform into strain-induced martensite, while high strength and impact toughness are associated with the high-volume fraction of transition carbides in the carbon-depleted martensitic matrix and a lack of transformation of RA to strain-induced martensite. The highest CVN impact energy was attained in the steel exhibiting transgranular quasi-cleavage fracture with the lowest effective grain size for brittle fracture. No correlation between strength, ductility and fracture toughness is observed in Q&P steels if these materials have distinct structural constituents. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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12 pages, 500 KiB  
Article
Directional Crystallization in the Presence of a Mushy Layer with Applications to the Earth’s Inner Core Boundary
by Dmitri V. Alexandrov, Irina V. Alexandrova, Margarita A. Nikishina, Alexey P. Malygin and Liubov V. Toropova
Crystals 2023, 13(9), 1361; https://doi.org/10.3390/cryst13091361 - 10 Sep 2023
Cited by 1 | Viewed by 1198
Abstract
We formulate the mathematical model of directional crystallization of a binary melt with a mushy layer (region) between purely solid and liquid phases. This model is complicated by melt convection and pressure-dependent phase transition temperature. Approximate analytical solutions to this nonlinear moving-boundary problem [...] Read more.
We formulate the mathematical model of directional crystallization of a binary melt with a mushy layer (region) between purely solid and liquid phases. This model is complicated by melt convection and pressure-dependent phase transition temperature. Approximate analytical solutions to this nonlinear moving-boundary problem are constructed. Namely, the concentration of impurity, fraction of solid phase, mushy region thickness, average fluid velocity, primary interdendritic spacing, mean radius of a chimney, and a characteristic distance between chimneys in a mushy region are found. Using this analytical solution, we describe the mushy region structure near the inner core boundary of the Earth, which is consistent with computer simulations and estimates existing in recent literature. A scheme illustrating the mushy region arrangement with chimneys at the inner core boundary of the Earth is presented. This arrangement based on the developed theory represents the novelty and importance of our study. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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15 pages, 3074 KiB  
Article
Current Design of Mixed-Ligand Complexes of Magnesium(II): Synthesis, Crystal Structure, Thermal Properties and Biological Activity against Mycolicibacterium Smegmatis and Bacillus Kochii
by Marina E. Nikiforova, Dmitriy S. Yambulatov, Yulia V. Nelyubina, Petr V. Primakov, Olga B. Bekker, Konstantin B. Majorov, Maxim A. Shmelev, Andrey V. Khoroshilov, Igor L. Eremenko and Irina A. Lutsenko
Crystals 2023, 13(9), 1306; https://doi.org/10.3390/cryst13091306 - 27 Aug 2023
Cited by 1 | Viewed by 1252
Abstract
The interaction of Mg2+ with 2-furoic acid (HFur) and oligopyridines, depending on the synthesis conditions, leads to the formation of mixed-ligand complexes [Mg(H2O)4(phen)]·2HFur·phen·H2O (1), [Mg(NO3)2(phen)2] (2) [...] Read more.
The interaction of Mg2+ with 2-furoic acid (HFur) and oligopyridines, depending on the synthesis conditions, leads to the formation of mixed-ligand complexes [Mg(H2O)4(phen)]·2HFur·phen·H2O (1), [Mg(NO3)2(phen)2] (2) and [Mg3(Fur)6(bpy)2]·3CH3CN (3); these structures were determined with an SC X-ray analysis. According to the X-ray diffraction data, in complex 1, obtained in ambient conditions, the magnesium cation coordinated four water molecules and one phenanthroline fragment, while in complexes 2 and 3 (synthesized in an inert atmosphere), the ligand environment of the complexing agent was represented by neutral oligopyridine molecules and acid anions. The thermal behavior of 1 and 2 was studied using a simultaneous thermal analysis (STA). The in vitro biological activity of complexes 1–3 was studied in relation to the non-pathogenic Mycolicibacterium smegmatis and the virulent strain Mycobacterium tuberculosis H37Rv. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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14 pages, 3767 KiB  
Article
Supramolecular Assemblies of Melamine-2-Thiobarbiturate and Melamine-Barbiturate-2-Thiobarbiturate: Experimental and Theoretical Studies
by Ivan V. Moskalenko, Vladimir V. Shilovskikh, Pavel V. Nesterov, Alexander S. Novikov, Malika Omarova, Roman V. Sadovnichii, Vladislav V. Gurzhiy, Nikita D. Orekhov and Ekaterina V. Skorb
Crystals 2023, 13(9), 1302; https://doi.org/10.3390/cryst13091302 - 25 Aug 2023
Viewed by 974
Abstract
In this work, we considered the formation of supramolecular assemblies of melamine-thiobarbiturate and melamine-barbiturate-thiobarbiturate. It is known that thiobarbituric acid can form many tautomers, as well as different motifs due to the change of C2=O to C2=S hydrogen bonds. We formed the crystal. [...] Read more.
In this work, we considered the formation of supramolecular assemblies of melamine-thiobarbiturate and melamine-barbiturate-thiobarbiturate. It is known that thiobarbituric acid can form many tautomers, as well as different motifs due to the change of C2=O to C2=S hydrogen bonds. We formed the crystal. The resulting crystals were studied with scanning electron microscopy (SEM), optical fluorescence microscopy, single crystal and powder (PXRD) X-ray diffraction analyses, and solid state nuclear magnetic resonance (ss NMR). These systems were theoretically studied using density functional theory (DFT) and classical molecular dynamics (MD) simulations. Interestingly, just as in the case of melamine barbiturate, during the crystallization process, hydrogen from the C5 moiety of thiobarbituric acid migrates to the melamine molecule. In addition, the resulting melamine thiobarbiturate crystals exhibit fluorescence behavior in the red region (~565–605 nm), while the melamine barbiturate crystals are fluorescent in the green region (512–542 nm). Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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14 pages, 7869 KiB  
Article
Compositional Variation and Crystal-Chemical Characterization of a Watermelon Variety of Tourmaline from Anjanabonoina, Central Madagascar
by Floriana Rizzo, Ferdinando Bosi, Gioacchino Tempesta and Giovanna Agrosì
Crystals 2023, 13(8), 1290; https://doi.org/10.3390/cryst13081290 - 21 Aug 2023
Viewed by 893
Abstract
A polychrome tourmaline crystal from Anjanabonoina pegmatite (Madagascar) was characterized using a multi-analytical approach. The sample showed a complex concentric zoning and a wide range of colors typical of the variety known as “watermelon”. The sample was cut perpendicularly to the c axis. [...] Read more.
A polychrome tourmaline crystal from Anjanabonoina pegmatite (Madagascar) was characterized using a multi-analytical approach. The sample showed a complex concentric zoning and a wide range of colors typical of the variety known as “watermelon”. The sample was cut perpendicularly to the c axis. The basal slice exhibits a rim characterized by narrow, differently colored layers parallel to the prism faces and a relatively homogeneous triangular core. Four main pronounced color zones were identified from the rim to core: a dark green rim (M1RVS); a pale green rim (M1RVC); a pale pink rim (M1CR); and a brownish yellow core (M1CG). Compositional variations in the basal slice were studied by scanning electron microscopy and electron microprobe analyses (WDS mode). The Li content was determined via micro-laser-induced breakdown spectroscopy. To deeply characterize the sample, single crystal structure refinement was also performed on fragments extracted from the four zones. The results show that the polychrome tourmaline sample consists of two different species: the three outer zones are Mn-rich fluor-liddicoatite, whereas the inner zone is Mn-rich fluor-elbaite. The structural and compositional characterization of the color zoning shows that each step of the tourmaline growth is related to a change in the geological environment. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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12 pages, 2589 KiB  
Communication
Zn(II) Metal–Organic Frameworks with a Long Spacer Ligand and a Tricarboxylate Coligand
by Dong Hee Lee and In-Hyeok Park
Crystals 2023, 13(8), 1266; https://doi.org/10.3390/cryst13081266 - 17 Aug 2023
Viewed by 728
Abstract
The preparations and structural characteristics of three-dimensional Zn(II) metal-organic frameworks (MOFs) with dipyridyl-olefin and tricarboxylate are reported. The solvothermal reactions of zinc(II) nitrate hexahydrate, 1,4-bis [2-(4-pyridyl)ethenyl]benzene (bpeb), and 4,4′,4″,-benzene-1,3,5-triyl-tris(benzoic acid) (H3btb) furnished three Zn(II) MOFs (1–3) with [...] Read more.
The preparations and structural characteristics of three-dimensional Zn(II) metal-organic frameworks (MOFs) with dipyridyl-olefin and tricarboxylate are reported. The solvothermal reactions of zinc(II) nitrate hexahydrate, 1,4-bis [2-(4-pyridyl)ethenyl]benzene (bpeb), and 4,4′,4″,-benzene-1,3,5-triyl-tris(benzoic acid) (H3btb) furnished three Zn(II) MOFs (1–3) with new topologies. Depending on the temperature or mole-ratio variations, self-interpenetrated [Zn2(bpeb)(btb)(OH)]·DMF·H2O (1), noninterpenetrated [Zn3(btb)2(bpeb)]·xSolvent (2), and fourfold interpenetrated [Zn2(Hbtb)2(bpeb)][Zn2(Hbtb)2(bpeb)][Zn4(Hbtb)4(bpeb)2] (3) structures were generated with different molecular building blocks. It is interesting that although all three MOFs contain the same metal cation, anion, and spacer ligand, they show different emissions due to structure and connectivity. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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22 pages, 6919 KiB  
Article
Crystal Structure Analysis, Stability, Phase Transformation and Selective Nucleation Mechanism of Fluralaner Polymorphs
by Guangyan Li, Ting Wang, Xin Huang, Na Wang, Lina Zhou, Beiqian Tian, Ziwei Feng, Ailing Liu, Yaling Li and Hongxun Hao
Crystals 2023, 13(8), 1241; https://doi.org/10.3390/cryst13081241 - 11 Aug 2023
Cited by 1 | Viewed by 1148
Abstract
To better understand and control the crystallization of different polymorphs, a comprehensive crystal structure analysis was conducted by using fluralaner as a model compound, and the thermodynamic stability, phase transformation, and selective nucleation mechanisms were studied. Various analytical techniques such as powder X-ray [...] Read more.
To better understand and control the crystallization of different polymorphs, a comprehensive crystal structure analysis was conducted by using fluralaner as a model compound, and the thermodynamic stability, phase transformation, and selective nucleation mechanisms were studied. Various analytical techniques such as powder X-ray diffraction, thermal analysis, and FT-IR spectra were used to comprehensively characterize Form I, Form Ⅱ, and Form III of fluralaner, and it was found that there is structural similarity between Form I and Form III, which was further confirmed by single crystal X-ray diffraction. However, it was found that Form Ⅱ had unique molecular conformation and packing pattern. The lattice energy was calculated by Materials Studio 7.0 and the thermodynamic stability of three forms was explored by phase transformation experiments, which suggested that the order of thermodynamic stability was Form Ⅱ > Form I > Form III. The selective nucleation of Form I and Form III with similar structure was studied through FT-IR spectra and molecular dynamics simulations. The results indicated that the addition of n-hexane may hinder the solute–solute interaction in the solution, thus resulting in the nucleation of different polymorphs. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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10 pages, 2580 KiB  
Article
Zinc(II) and Copper(II) Complexes of 4-Styrylpyridine and 1-Adamantanecarboxylic Acid: Syntheses, Crystal Structures, and Photopolymerization
by Dong Hee Lee, Jaewook An, Jihye Oh and In-Hyeok Park
Crystals 2023, 13(8), 1226; https://doi.org/10.3390/cryst13081226 - 09 Aug 2023
Cited by 1 | Viewed by 773
Abstract
A combination of 4-styrylpyridine (spy) and 1-adamantanecarboxylic acid (Hadc) was employed in the assembly reactions with Zn(II) and Cu(II) nitrates. The photoreactivity of the products was compared and discussed on the basis of the structure–function relationship. Zinc(II) complex 1 is a trinuclear species [...] Read more.
A combination of 4-styrylpyridine (spy) and 1-adamantanecarboxylic acid (Hadc) was employed in the assembly reactions with Zn(II) and Cu(II) nitrates. The photoreactivity of the products was compared and discussed on the basis of the structure–function relationship. Zinc(II) complex 1 is a trinuclear species of type [Zn3(spy)2(adc)6] in which three zinc(II) atoms are linearly arranged, with two adjacent zinc(II) atoms linked by three bridging carboxylates. Two spy ligands occupy both terminal positions, yielding the overall structure of a six-bladed windmill. Copper(II) complex 2, [Cu(spy)2(adc)2][Cu2(spy)2(adc)4]·2DMF, is an inorganic cocrystal comprising a mononuclear complex with a trans square planar geometry and a dinuclear complex with a paddle-wheel structure. In the photoreaction experiments characterized by 1H NMR spectroscopy, the zinc(II) complex was found to be photoinert, while the copper(II) complex was photoreactive to form a cyclobutene ring via the [2+2] photodimerization between two spy ligands, resulting in the preparation of a one-dimensional chain as a coordination polymer. The separations of the C=C bond pair obtained from the crystal structures for both products also support their photoreactivity. For example, the spy ligands from two adjacent monocopper(II) complexes are aligned in a head-to-tail manner with the separation of 3.899 Å between the C=C bond pair, satisfying the so-called Schmidt criteria (<4.2 Å). However, no other products satisfy this condition. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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40 pages, 20878 KiB  
Article
Simulation of the Void Shape Evolution of High-Temperature Annealed Silicon Structures by means of a Custom Level-Set Formulation
by Constantino Grau Turuelo and Cornelia Breitkopf
Crystals 2023, 13(6), 863; https://doi.org/10.3390/cryst13060863 - 24 May 2023
Viewed by 1004
Abstract
The control and prediction of morphological changes in annealed void microstructures is an essential and powerful tool for different semiconductor applications, for example, as part of the production of pressure sensors, resonators, or other silicon structures. In this work, with a focus on [...] Read more.
The control and prediction of morphological changes in annealed void microstructures is an essential and powerful tool for different semiconductor applications, for example, as part of the production of pressure sensors, resonators, or other silicon structures. In this work, with a focus on the void shape evolution of silicon, a novel simulation approach based on the level-set method is introduced to predict the continuous transformation of initial etched nano/micro-sized cylindrical structures at different annealing conditions. The developed model, which is based on a surface diffusion formulation and built in COMSOL Multiphysics® (Stockholm, Sweden), is introduced and compared to experimental literature data as well as with other analytical approaches. Some advantages of the presented model include the capability of simulating other materials under similar phenomena, the simulation of any possible initial geometry, and the visualization of intermediate steps during the annealing processing. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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Review

Jump to: Research

22 pages, 3972 KiB  
Review
Basic Modelling of General Strength and Creep Properties of Alloys
by Rolf Sandström
Crystals 2024, 14(1), 21; https://doi.org/10.3390/cryst14010021 - 25 Dec 2023
Viewed by 793
Abstract
There are excellent methods for modelling physical and elastic properties, for example, those based on ab initio atomistic procedures. For mechanical properties that are controlled by the motion of the dislocations, such methods have not been available in the past. One has been [...] Read more.
There are excellent methods for modelling physical and elastic properties, for example, those based on ab initio atomistic procedures. For mechanical properties that are controlled by the motion of the dislocations, such methods have not been available in the past. One has been forced to resort to fitting the experimental data with empirical methods by involving a number of adjustable parameters. However, in recent years, methods based on physical principles have been developed for a number of mechanical properties. These methods can predict properties accurately without the use of fitting parameters. A review of such methods will be given, for example, for the modelling of creep deformation in metallic materials. It will be demonstrated that some properties can be described over a wide range of temperatures and strain rates. The advantage of these new methods is that they can be used for prediction, identification of mechanisms and extrapolation of results for new conditions. Full article
(This article belongs to the Special Issue Feature Papers in Crystals 2023)
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