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2 pages, 165 KiB

Open AccessEditorial

First-Principle and Atomistic Modelling in Materials Science

by Matthias Posselt

Materials 2021, 14(6), 1469; https://doi.org/10.3390/ma14061469 - 17 Mar 2021

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Abstract

In the last two decades, the importance of Computational Materials Science has continuously increased due to the steadily growing availability of computer power [...] Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

Research

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10 pages, 3158 KiB

Open AccessArticle

Effects of Transition Element Additions on the Interfacial Interaction and Electronic Structure of Al(111)/6H-SiC(0001) Interface: A First-Principles Study

by Changqing Wang, Weiguang Chen and Jingpei Xie

Materials 2021, 14(3), 630; https://doi.org/10.3390/ma14030630 - 29 Jan 2021

Cited by 9 | Viewed by 2010

Abstract

In this work, the effects of 20 transition element additions on the interfacial adhesion energy and electronic structure of Al(111)/6H-SiC(0001) interfaces have been studied by the first-principles method. For pristine Al(111)/6H-SiC(0001) interfaces, both Si-terminated and C-terminated interfaces have covalent bond characteristics. The C-terminated [...] Read more.

In this work, the effects of 20 transition element additions on the interfacial adhesion energy and electronic structure of Al(111)/6H-SiC(0001) interfaces have been studied by the first-principles method. For pristine Al(111)/6H-SiC(0001) interfaces, both Si-terminated and C-terminated interfaces have covalent bond characteristics. The C-terminated interface has higher binding energy, which is mainly due to the stronger covalent bond formed by the larger charge transfer between C and Al. The results show that the introduction of many transition elements, such as 3d transitional group Mn, Fe, Co, Ni, Cu, Zn and 4d transitional group Tc, Ru, Rh, Pd, Ag, can improve the interfacial adhesion energy of the Si-terminated Al(111)/6H-SiC(0001) interface. However, for the C-terminated Al(111)/6H-SiC(0001) interface, only the addition of Co element can improve the interfacial adhesion energy. Bader charge analysis shows that the increase of interfacial binding energy is mainly attributed to more charge transfer. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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14 pages, 2827 KiB

Open AccessArticle

Strengthening Effect of Nb on Ferrite Grain Boundary in X70 Pipeline Steel

by Zhongyi Li, Zhipeng Li and Wenhuai Tian

Materials 2021, 14(1), 61; https://doi.org/10.3390/ma14010061 - 25 Dec 2020

Cited by 10 | Viewed by 1961

Abstract

Understanding the strengthening effect of niobium on ferrite grain boundaries from the perspective of valence electron structures will help to use niobium and other microalloying elements more effectively to improve the performance of steel materials. In this paper, the effect of niobium element [...] Read more.

Understanding the strengthening effect of niobium on ferrite grain boundaries from the perspective of valence electron structures will help to use niobium and other microalloying elements more effectively to improve the performance of steel materials. In this paper, the effect of niobium element on ferrite grain boundary strengthening is studied based on microstructure analysis at the nanometer scale. The enrichment of niobium in pipeline steel at ferrite boundary was observed by a three-dimensional atomic probe test. Segregation of Nb is observed in the ferrite grain boundaries of X70 steel, and its maximum concentration is 0.294–0.466 at.%. The charges in the occupancy of the Fe 3d state in grain and grain boundary were 7.23 and 7.37, respectively, based on quantitative analysis of electron energy loss spectra (EELS). The first-principle calculation suggests that the charges in the occupancy of 3d state for grain boundary iron are 6.57 and 6.68, respectively, before and after the Nb doping (with an increase of 1.67%), which reveals a similar trend to that of the EELS results. Through Nb alloying, the 3d valence electronic density of the state of Fe in grain boundary moves to a lower energy, which can reduce the total energy of the system and make the grain boundary more stable. Meanwhile, the charges in the occupancy of the 3d state for Fe in the grain boundary increases, providing more electrons for grain boundary bonding. These improve the strength and toughness of the material. This work provides a fundamental understanding for pipeline steel strengthening by element alloying. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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14 pages, 7571 KiB

Open AccessArticle

Deformation Behavior of Nanocrystalline Body-Centered Cubic Iron with Segregated, Foreign Interstitial: A Molecular Dynamics Study

by Ahmed Tamer AlMotasem, Matthias Posselt and Tomas Polcar

Materials 2020, 13(23), 5351; https://doi.org/10.3390/ma13235351 - 25 Nov 2020

Cited by 4 | Viewed by 1585

Abstract

In the present work, modified embedded atom potential and large-scale molecular dynamics’ simulations were used to explore the effect of grain boundary (GB) segregated foreign interstitials on the deformation behavior of nanocrystalline (nc) iron. As a case study, carbon and nitrogen (about 2.5 [...] Read more.

In the present work, modified embedded atom potential and large-scale molecular dynamics’ simulations were used to explore the effect of grain boundary (GB) segregated foreign interstitials on the deformation behavior of nanocrystalline (nc) iron. As a case study, carbon and nitrogen (about 2.5 at.%) were added to (nc) iron. The tensile test results showed that, at the onset of plasticity, grain boundary sliding mediated was dominated, whereas both dislocations and twinning were prevailing deformation mechanisms at high strain. Adding C/N into GBs reduces the free excess volume and consequently increases resistance to GB sliding. In agreement with experiments, the flow stress increased due to the presence of carbon or nitrogen and carbon had the stronger impact. Additionally, the simulation results revealed that GB reduction and suppressing GBs’ dislocation were the primary cause for GB strengthening. Moreover, we also found that the stress required for both intragranular dislocation and twinning nucleation were strongly dependent on the solute type. Full article

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22 pages, 5901 KiB

Open AccessArticle

Structural, Electronic, and Optical Properties of CsPb(Br_1−xCl_x)₃ Perovskite: First-Principles Study with PBE–GGA and mBJ–GGA Methods

by Hamid M. Ghaithan, Zeyad. A. Alahmed, Saif M. H. Qaid and Abdullah S. Aldwayyan

Materials 2020, 13(21), 4944; https://doi.org/10.3390/ma13214944 - 03 Nov 2020

Cited by 24 | Viewed by 3601

Abstract

The effect of halide composition on the structural, electronic, and optical properties of CsPb(Br_1−xCl_x)₃ perovskite was investigated in this study. When the chloride (Cl) content of x was increased, the unit cell volume decreased with a linear function. [...] Read more.

The effect of halide composition on the structural, electronic, and optical properties of CsPb(Br_1−xCl_x)₃ perovskite was investigated in this study. When the chloride (Cl) content of x was increased, the unit cell volume decreased with a linear function. Theoretical X-ray diffraction analyses showed that the peak (at 2θ = 30.4°) shifts to a larger angle (at 2θ = 31.9°) when the average fraction of the incorporated Cl increased. The energy bandgap (E_g) was observed to increase with the increase in Cl concentration. For x = 0.00, 0.25, 0.33, 0.50, 0.66, 0.75, and 1.00, the E_g values calculated using the Perdew–Burke–Ernzerhof potential were between 1.53 and 1.93 eV, while those calculated using the modified Becke−Johnson generalized gradient approximation (mBJ–GGA) potential were between 2.23 and 2.90 eV. The E_g calculated using the mBJ–GGA method best matched the experimental values reported. The effective masses decreased with a concentration increase of Cl to 0.33 and then increased with a further increase in the concentration of Cl. Calculated photoabsorption coefficients show a blue shift of absorption at higher Cl content. The calculations indicate that CsPb(Br_1−xCl_x)₃ perovskite could be used in optical and optoelectronic devices by partly replacing bromide with chloride. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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10 pages, 2453 KiB

Open AccessArticle

Effects of Monovacancy and Divacancies on Hydrogen Solubility, Trapping and Diffusion Behaviors in fcc-Pd by First Principles

by Bao-Long Ma, Yi-Yuan Wu, Yan-Hui Guo, Wen Yin, Qin Zhan, Hong-Guang Yang, Sheng Wang and Bao-Tian Wang

Materials 2020, 13(21), 4876; https://doi.org/10.3390/ma13214876 - 30 Oct 2020

Cited by 5 | Viewed by 1943

Abstract

The hydrogen blistering phenomenon is one of the key issues for the target station of the accelerator-based neutron source. In the present study, the effect of monovacancies and divacancies defects on the solution, clustering and diffusion behaviors of H impurity in fcc-Pd were [...] Read more.

The hydrogen blistering phenomenon is one of the key issues for the target station of the accelerator-based neutron source. In the present study, the effect of monovacancies and divacancies defects on the solution, clustering and diffusion behaviors of H impurity in fcc-Pd were studied through first principles calculations. Our calculations prove that vacancies behave as an effective sink for H impurities. We found that, although the H-trap efficiency of the larger vacancy defect was reduced, its H-trap ability strengthened. There is a short-ranged area around the vacancy defects in which H impurities tend to diffuse to vacancy defects, gather and form hydrogen bubbles. Therefore, the characteristic of large vacancy defects formation in materials should be considered when screening anti-blistering materials for neutron-producing targets or when designing radiation resistant composite materials. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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13 pages, 5733 KiB

Open AccessArticle

Dynamics Studies of Nitrogen Interstitial in GaN from Ab Initio Calculations

by Huan He, Wenbo Liu, Pengbo Zhang, Wenlong Liao, Dayin Tong, Lin Yang, Chaohui He, Hang Zang and Hongxiang Zong

Materials 2020, 13(16), 3627; https://doi.org/10.3390/ma13163627 - 17 Aug 2020

Cited by 7 | Viewed by 2221

Abstract

Understanding the properties of defects is crucial to design higher performance semiconductor materials because they influence the electronic and optical properties significantly. Using ab initio calculations, the dynamics properties of nitrogen interstitial in GaN material, including the configuration, migration, and interaction with vacancy [...] Read more.

Understanding the properties of defects is crucial to design higher performance semiconductor materials because they influence the electronic and optical properties significantly. Using ab initio calculations, the dynamics properties of nitrogen interstitial in GaN material, including the configuration, migration, and interaction with vacancy were systematically investigated in the present work. By introducing different sites of foreign nitrogen atom, the most stable configuration of nitrogen interstitial was calculated to show a threefold symmetry in each layer and different charge states were characterized, respectively. In the researches of migration, two migration paths, in-plane and out-of-plane, were considered. With regards to the in-plane migration, an intermediated rotation process was observed first time. Due to this rotation behavior, two different barriers were demonstrated to reveal that the migration is an anisotropic behavior. Additionally, charged nitrogen Frenkel pair was found to be a relatively stable defect complex and its well separation distance was about 3.9 Å. Part of our results are in good agreement with the experimental results, and our work provides underlying insights of the identification and dynamics of nitrogen interstitial in GaN material. This study of defects in GaN material is useful to establish a more complete theory and improve the performance of GaN-based devices. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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12 pages, 2498 KiB

Open AccessArticle

First-Principles Study on III-Nitride Polymorphs: AlN/GaN/InN in the Pmn2₁ Phase

by Zheren Zhang, Changchun Chai, Wei Zhang, Yanxing Song, Linchun Kong and Yintang Yang

Materials 2020, 13(14), 3212; https://doi.org/10.3390/ma13143212 - 19 Jul 2020

Cited by 7 | Viewed by 2294

Abstract

The structural, mechanical, and electronic properties, as well as stability, elastic anisotropy and effective mass of AlN/GaN/InN in the Pmn2₁ phase were determined using density functional theory (DFT). The phonon dispersion spectra and elastic constants certify the dynamic and mechanical stability [...] Read more.

The structural, mechanical, and electronic properties, as well as stability, elastic anisotropy and effective mass of AlN/GaN/InN in the Pmn2₁ phase were determined using density functional theory (DFT). The phonon dispersion spectra and elastic constants certify the dynamic and mechanical stability at ambient pressure, and the relative enthalpies were lower than those of most proposed III-nitride polymorphs. The mechanical properties reveal that Pmn2₁-AlN and Pmn2₁-GaN possess a high Vickers hardness of 16.3 GPa and 12.8 GPa. Pmn2₁-AlN, Pmn2₁-GaN and Pmn2₁-InN are all direct semiconductor materials within the HSE06 hybrid functional, and their calculated energy band gaps are 5.17 eV, 2.77 eV and 0.47 eV, respectively. The calculated direct energy band gaps and mechanical properties of AlN/GaN/InN in the Pmn2₁ phase reveal that these three polymorphs may possess great potential for industrial applications in the future. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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17 pages, 3757 KiB

Open AccessArticle

First-Principles Study on Structural, Mechanical, Anisotropic, Electronic and Thermal Properties of III-Phosphides: XP (X = Al, Ga, or In) in the P6₄22 Phase

by Junjie Miao, Changchun Chai, Wei Zhang, Yanxing Song and Yintang Yang

Materials 2020, 13(3), 686; https://doi.org/10.3390/ma13030686 - 04 Feb 2020

Cited by 12 | Viewed by 2372

Abstract

The structural, mechanical, electronic, and thermal properties, as well as the stability and elastic anisotropy, of XP (X = Al, Ga, or In) in the P6₄22 phase were studied via density functional theory (DFT) in this work. P [...] Read more.

The structural, mechanical, electronic, and thermal properties, as well as the stability and elastic anisotropy, of XP (X = Al, Ga, or In) in the P6₄22 phase were studied via density functional theory (DFT) in this work. P6₄22-XP (X = Al, Ga, or In) are dynamically and thermodynamically stable via phonon spectra and enthalpy. At 0 GPa, P6₄22-XP (X = Al, Ga, or In) are more rigid than F

\bar{4} 3

m-XP (X = Al, Ga, or In), of which P6₄22-XP (X = Al or Ga) are brittle and P6₄22-InP is ductile. In the same plane (except for (001)-plane), P6₄22-AlP and P6₄22-InP exhibit the smallest and the largest anisotropy, respectively, and P6₄22-XP (X = Al, Ga, or In) is isotropic in the (001)-plane. In addition, Al, Ga, In, and P bonds bring different electrical properties: P6₄22-InP exhibits a direct band gap (0.42 eV) with potential application for an infrared detector, whereas P6₄22-XP (X = Al or Ga) exhibit indirect band gap (1.55 eV and 0.86 eV). At high temperature (approaching the melting point), the theoretical minimum thermal conductivities of P6₄22-XP (X = Al, Ga, or In) are AlP (1.338 W∙m⁻¹∙K⁻¹) > GaP (1.058 W∙m⁻¹∙K⁻¹) > InP (0.669 W∙m⁻¹∙K⁻¹), and are larger than those of F

\bar{4} 3

m-XP (X = Al, Ga, or In). Thus, P6₄22-XP (X = Al, Ga, or In) have high potential application at high temperature. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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12 pages, 2464 KiB

Open AccessArticle

Relationship between the Behavior of Hydrogen and Hydrogen Bubble Nucleation in Vanadium

by Zhengxiong Su, Sheng Wang, Chenyang Lu and Qing Peng

Materials 2020, 13(2), 322; https://doi.org/10.3390/ma13020322 - 10 Jan 2020

Cited by 4 | Viewed by 2451

Abstract

Hydrogen plays a significant role in the microstructure evolution and macroscopic deformation of materials, causing swelling and surface blistering to reduce service life. In the present work, the atomistic mechanisms of hydrogen bubble nucleation in vanadium were studied by first-principles calculations. The interstitial [...] Read more.

Hydrogen plays a significant role in the microstructure evolution and macroscopic deformation of materials, causing swelling and surface blistering to reduce service life. In the present work, the atomistic mechanisms of hydrogen bubble nucleation in vanadium were studied by first-principles calculations. The interstitial hydrogen atoms cannot form significant bound states with other hydrogen atoms in bulk vanadium, which explains the absence of hydrogen self-clustering from the experiments. To find the possible origin of hydrogen bubble in vanadium, we explored the minimum sizes of a vacancy cluster in vanadium for the formation of hydrogen molecule. We show that a freestanding hydrogen molecule can form and remain relatively stable in the center of a 54-hydrogen atom saturated 27-vacancy cluster. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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8 pages, 1501 KiB

Open AccessArticle

Influence of Mixed Valence on the Formation of Oxygen Vacancy in Cerium Oxides

by Gege Zhou, Wentong Geng, Lu Sun, Xue Wang, Wei Xiao, Jianwei Wang and Ligen Wang

Materials 2019, 12(24), 4041; https://doi.org/10.3390/ma12244041 - 05 Dec 2019

Cited by 14 | Viewed by 2719

Abstract

Ceria is one of the most important functional rare-earth oxides with wide industrial applications. Its amazing oxygen storage/release capacity is attributed to cerium’s flexible valence conversion between 4+ and 3+. However, there still exists some debate on whether the valence conversion is due [...] Read more.

Ceria is one of the most important functional rare-earth oxides with wide industrial applications. Its amazing oxygen storage/release capacity is attributed to cerium’s flexible valence conversion between 4+ and 3+. However, there still exists some debate on whether the valence conversion is due to the Ce-4f electron localization-delocalization transition or the character of Ce–O covalent bonds. In this work, a mixed valence model was established and the formation energies of oxygen vacancies and electronic charges were obtained by density functional theory calculations. Our results show that the formation energy of oxygen vacancy is affected by the valence state of its neighboring Ce atom and two oxygen vacancies around a Ce⁴⁺ in CeO₂ have a similar effect to a Ce³⁺. The electronic charge difference between Ce³⁺ and Ce⁴⁺ is only about 0.4e. Therefore, we argue that the valence conversion should be understood according to the adjustment of the ratio of covalent bond to ionic bond. We propose that the formation energy of oxygen vacancy be used as a descriptor to determine the valence state of Ce in cerium oxides. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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8 pages, 2538 KiB

Open AccessLetter

The Interfacial Characteristics of Graphene/Al₄C₃ in Graphene/AlSi10Mg Composites Prepared by Selective Laser Melting: First Principles and Experimental Results

by Wenjie Zhao, Zhanyong Zhao, Peikang Bai, Lizheng Zhang, Bing Han and Wenbo Du

Materials 2020, 13(3), 702; https://doi.org/10.3390/ma13030702 - 04 Feb 2020

Cited by 12 | Viewed by 2496

Abstract

The Al₄C₃ phase was precipitated via a reaction of graphene (Gr) with Al during selective laser melting (SLM). The interfacial nature of the Gr (0001)/Al₄C₃ (0001) interface was determined using the first-principle calculation. The simulation results showed [...] Read more.

The Al₄C₃ phase was precipitated via a reaction of graphene (Gr) with Al during selective laser melting (SLM). The interfacial nature of the Gr (0001)/Al₄C₃ (0001) interface was determined using the first-principle calculation. The simulation results showed that the influence of the stacking site on the interfacial structure was limited and the Al-termination interface presented a more stable structure than the C-termination interface. The Al-termination-CH site interface had the largest work of adhesion (6.28 J/m²) and the smallest interfacial distance (2.02 Å) among the four interfacial structures. Mulliken bond population analysis showed that the bonding of the Al-termination interface was a mixture of covalent and ionic bonds and there was no chemical bonding in the C-termination interface. Full article

(This article belongs to the Special Issue First-Principle and Atomistic Modelling in Materials Science)

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