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Article

Adsorption Tuning of Polarity and Magnetism in AgCr2S4 Monolayer

School of Physics, Southeast University, Nanjing 211189, China
*
Authors to whom correspondence should be addressed.
Materials 2023, 16(8), 3058; https://doi.org/10.3390/ma16083058
Submission received: 1 March 2023 / Revised: 3 April 2023 / Accepted: 11 April 2023 / Published: 12 April 2023
(This article belongs to the Special Issue First-Principles Calculations of 2D Magnetic Materials)

Abstract

:
As a recent successfully exfoliated non-van der Waals layered material, AgCrS2 has received a lot of attention. Motivated by its structure-related magnetic and ferroelectric behavior, a theoretical study on its exfoliated monolayer AgCr2S4 has been carried out in the present work. Based on density functional theory, the ground state and magnetic order of monolayer AgCr2S4 have been determined. The centrosymmetry emerges upon two-dimensional confinement and thus eliminates the bulk polarity. Moreover, two-dimensional ferromagnetism appears in the CrS2 layer of AgCr2S4 and can persist up to room temperature. The surface adsorption has also been taken into consideration, which shows a nonmonotonic effect on the ionic conductivity through ion displacement of the interlayer Ag, but has little impact on the layered magnetic structure.

1. Introduction

Recently, a large number of new two-dimensional (2D) functional materials have been synthesized and reported, including those with intrinsic ferroelectric and long-range spin orders, which have greatly stimulated people’s research enthusiasm for 2D ferroic materials [1,2,3,4,5,6,7,8,9,10,11,12].
Inspired by graphene, most previous research has focused on 2D layered van der Waals (vdW) materials, whose atomic-thin layers can be easily obtained by mechanical exfoliation due to their weak vdW interlayer bonding [13,14,15]. With the development of 2D research, more feasible approaches emerge. As a supplement to mechanical cleavage, those methods can artificially open a gap between layers of non-vdW materials through selective etching or ionic intercalation. The 2D layer can then be obtained through post-procedure. The typical representatives prepared by chemical etching and intercalation are MXene and AM2X4, respectively [16,17]. Since then, non-vdW layered materials soon became another emerging branch of 2D materials, especially those with intrinsic ferroelectricity, long-range spin orders, or both. For example, NaCrX2 with adjustable conductivity and ACr2S4 (A = Li, Na, K, Rb) nanosheets with multiferroic properties have been reported recently [18,19].
AgCrS2 is one such layered material with both long-range magnetic order and ferroelectricity. This compound was synthesized in 1957 [20]. It is composed of an alternative stacking of edge-sharing octahedra CrS2 layers and Ag ion layers along the c-axis in a trigonal lattice (R3m) around room temperature. When cooled down to TN (about 40 K), the lattice changes to monoclinic (Cm), accompanied by the emergence of in-plane double stripes (DS) antiferromagnetic (AFM) order [21,22]. The ferroelectricity originates from the off-centering displacement of Ag ions. Several experimental works found that this polarization is closely related to the structural and magnetic transition [21,22]. Recently, the monolayer AgCr2S4, consisting of a single Ag layer sandwiched between two CrS2 layers, was successfully exfoliated from AgCrS2 bulk [17]. Interest has been aroused [23,24], mainly focusing on the magnetic and ferroelectric properties of single-layer AgCr2S4. However, the specific structure of the monolayer, the possible surface adsorption after peeling, and their effects on material properties have not been well explored.
In this work, based on density functional theory (DFT), the magnetic ground state of bulk AgCrS2 has been checked. Our calculation results on bulk are consistent with recent experimental observations, which not only ensure the feasibility of our calculation but also form a solid basis for the following study on its monolayer. The structural, magnetic, and electronic properties of AgCr2S4 monolayer have been further studied. Unexpectedly, the polar symmetry inherited from the parent phase could not be preserved during optimization. Moreover, ferromagnetic (FM) order appears in the in-plane Cr triangular lattice with relatively weak interplane AFM coupling. The situation changes when hydrogen adsorption is taken into consideration. After adsorption, the intralayer FM and interlayer AFM ground state remains unchanged, but the structural symmetry is altered along with its ferroelectricity and ionic transport behavior.

2. Methods

Our DFT calculations were performed using Vienna ab initio Simulation Package (VASP) [25,26]. The electronic interactions were described by projector-augmented-wave (PAW) pseudo-potentials, with semicore states treated as valence states [27]. The exchange and correlation were treated using Perdew–Burke–Ernzerhof (PBE) parametrization of the generalized gradient approximation (GGA) [28]. To properly describe the correlated electrons, the GGA+U method was adopted, and the on-site Hubbard Ueff was imposed on Cr’s 3d orbitals using the Dudarev approach for all calculations [29]. The plane-wave cutoff energy was set to 500 eV. The Monkhorst−Pack K-point meshes were chosen as 2 × 8 × 4 and 7 × 7 × 1 for bulk and monolayer calculations, respectively. Exchange coefficients and magnetic ground states for the monolayer were estimated based on a 2 × 4 × 1 supercell with various magnetic orders. The convergent criterion for the energy was set to 10−5 eV, and that of the Hellman–Feynman forces during structural relaxation was 0.01 eV/Å.
In the study of the monolayer structure, a vacuum layer of 20 Å was added along the c-axis direction to avoid the interaction between two neighboring slices. The possible switching paths between different structure phases were evaluated by the nudged elastic band (NEB) method [30]. To estimate the Curie temperature and the temperature evolution of magnetic properties, the Markov-chain Monte Carlo (MC) method with Metropolis algorithm was employed to simulate the magnetic ordering [31]. The MC simulation was performed on a 40 × 40 lattice with periodic boundary conditions, and larger lattices were also tested to confirm the physical results. The simulations were performed with 20,000 equilibration steps and 80,000 averaging steps. All MC simulations are gradually cooled down from the initial disordered state at high temperature to the low temperature under investigation.

3. Results

3.1. AgCrS2 Bulk Properties

As mentioned above, the low-temperature bulk crystal belongs to the Cm space group without spatial inversion symmetry. Its intrinsic layered feature is illustrated in Figure 1a. The Cr3+ ions located at the center of CrS6 octahedra form a triangular magnetic lattice within each CrS2 layer. Recently, an in-plane collinear magnetic structure has been reported, showing DS pattern (as shown in Figure 1c) with AFM coupling in between [22,32]. The magnetic ordering and structural transition occur simultaneously, accompanied by the emergence of ferroelectricity, indicating the strong connection between magnetic, ferroelectric, and structural properties [32,33,34,35].
To determine the magnetic ground state, three common collinear configurations on the triangular lattice, as depicted in Figure 1c, have been taken into account in addition to the reported DS order. Besides, in order to study the interlayer magnetic coupling, the intralayer FM and interlayer AFM (A-AFM) configuration has also been considered. Our calculation results show that the DS-AFM pattern is indeed the magnetic ground state when Ueff is less than 0.8 eV (Figure 1d). The total energy of AFM zigzag and stripe configurations are always higher than that of DS-AFM and are almost insensitive to the Ueff value. In contrast, the energy of A-AFM and FM decrease with increasing Ueff, showing a similar trend. The A-AFM order is energetically more favorable than FM, and will even replace DS-AFM as the ground state when Ueff is larger than 0.8 eV. Obviously, a specific Ueff value (i.e., 0.6 eV) is vital in precisely reproducing AgCrS2 bulk properties. The local magnetic moment increases with the increase in Ueff, reaching 2.86 µB/Cr at 0.6 eV, which is consistent with previously reported value [22]. Moreover, the optimized lattice constants (a = 13.83 Å, b = 3.54 Å, and c = 7.13 Å) are in good agreement with the experimental data [22,24]. Therefore, it will be adopted in the following calculations by default.

3.2. AgCr2S4 Monolayer

Recently, AgCrS2 was successfully exfoliated into 2D nanosheets by Peng et al. through ion intercalation [17]. These 2D sheets can be thinned down to a monolayer containing one Ag ion layer sandwiched between two CrS2 layers. As can be seen from Figure 2a,b, the edge-sharing octahedral framework is inherited in CrS2 layers, while the relative displacement of the center Ag ion will give rise to two distinct structural phases (i.e., the asymmetric α phase and the centrosymmetric β phase). The detailed structural information is shown in Table S1 and Figure S1. In the following, we will focus on the structural, magnetic, and electronic properties of AgCr2S4 monolayer.
To find the ground state of AgCr2S4 monolayer, the total energies of different magnetic orders mentioned earlier have been calculated based on the above two structural phases. The calculation results have been summarized in Table 1. Obviously, the energy of the β phase is always lower than that of the α phase, presenting a clear tendency to restore the central symmetry of the 2D single layer, contrary to its parent bulk phase.
Our results also indicate that the magnetic Cr ions in each CrS2 layer tend to couple ferromagnetically and show no sensitivity to the above two structural phases. This structure-insensitive FM behavior, in contrast with its bulk form, can be reasonably interpreted on the basis of the d orbital occupation of Cr. In the AgCrS2 bulk, Cr3+ ion is in the 3d3 configuration. According to the Goodenough–Kanamori–Anderson (GKA) rules [36,37,38], the half-filled t2g orbitals give rise to AFM direct exchange, while the p orbital intermediated Cr-S-Cr super exchange favors FM coupling. It is the competing exchange interactions that make the bulk magnetic order structurally related. In contrast, from the change of chemical formula before and after exfoliation, the Cr ion in AgCr2S4 monolayer is in the mixed valence state (Cr27+). The hole hopping between neighboring Cr’s d orbitals gives rise to the strong FM tendency and is insensitive to structural details.
To characterize this in-plane triangular magnetic lattice, the classical Heisenberg spin model is adopted, which can be constructed as
H = J 1 < i , j > S i · S j + J 2 [ i , k ] S i · S k + i K c ( S i z ) 2 + K b ( S i y ) 2
where Si is the normalized spin (|S| = 1) on the Cr site i. J1 and J2 correspond to the in-plane exchange constants between the nearest-neighbor (NN) and the next-nearest-neighbor (NNN) interactions, as labeled in Figure 2b, respectively. Kb/c stands for the single-ion magnetocrystalline anisotropy along the b-/c-axis, respectively. Based on the ground structure (β phase), these exchange coefficients can be extracted by comparing DFT energy with different spin orders. Specifically, in a 2 × 4 × 1 supercell, the energy of these magnetic states can be expressed as
E FM = E 0 + 3 J 1 + 3 J 2 E DS = E 0 + J 1 J 2 E Z = E 0 J 1 + J 2
where E0 is the nonmagnetic energy. The derived parameters are summarized in Table 2. According to our estimation, the NN exchange interactions are FM and dominated, as expected from our previous analysis. The NNN exchange constant J2 is relatively weak due to its indirect and long-distance bonding. Based on these exchange parameters, MC simulations were employed to determine the Curie temperature. Additionally, the magnetic susceptibility was calculated. The system reaches equilibrium at a given temperature, the magnetization M and magnetic susceptibility χ are calculated as [39]
M = 1 N i = 1 N S i
χ = M 2 M 2 k B T
where N represents the total number of spin sites. Given the exact solution of the spin Hamiltonian, TC can be estimated from the peak position of the specific magnetic susceptibility χ (or the maximum slop point of magnetization M). MC results are shown in Figure 2c, indicating that the magnetic transition temperature is above room temperature, much higher than its parent bulk, as expected from its changed and mixed valence of Cr ions. Our MC simulation have also been tested on multi-size lattices to exclude the finite size effect. As shown in Figure S2, the magnetization and susceptibility curve are not sensitive to lattice size, and the Curie temperature shows no obvious scale effect.
Since the AgCr2S4 monolayer contains two CrS2 layers, the interlayer coupling has also been considered. Our calculation shows that the interlayer AFM coupling is energetically more favorable than FM coupling, although the energy difference is quite limited (within 3 meV). After exfoliation, the CrS2-CrS2 interlayer coupling decreases with the increase in the interlayer spacing (from 4.60 Å to 4.76 Å), which is consistent with the intuition. These weakly coupled 2D FM triangular lattices in the AgCr2S4 monolayer may provide a new approach for magnetic regulation in spintronic devices.
The electronic densities of states (DOS) of AgCrS2 bulk and AgCr2S4 monolayer are shown in Figure 3. The parent bulk phase exhibits insulating characteristics with a moderate gap of about 1.5 eV. The states near the Fermi level mainly originate from Cr’s 3d orbitals. In the AgCr2S4 monolayer, the stripping induced hole-doping causes a negative shift in the Fermi level, and therefore closes the gap. Meanwhile, Cr’s dominant contribution to the Fermi level is not affected upon peeling.
In addition, we also verified the mechanical stability of AgCr2S4. The in-plane elastic constants and various mechanical parameters are summarized in Tables S2 and S3, respectively. Our calculation results prove that AgCr2S4 is a soft and malleable material, similar to its three-dimensional counterpart [40]. The schematic diagrams of Young’s modulus, shear modulus, and Poisson’s ratio are given in Figure S5.

3.3. H Adsorption Effect

The AgCr2S4 monolayer is synthesized through wet chemical exfoliation of bulk AgCrS2. Analogous to MXene, the high surface area to volume ratio and the unsaturated bonds of the outer layer sulfur ions may lead to the adsorption of ions at surface sites during preparation. Thus, the hydrogen adsorption and its effect on structural and magnetic properties of AgCr2S4 monolayer have been investigated. First, the unilateral passivation is considered. As labeled in Figure 4a,b, there are ten possible adsorption sites. According to our calculations, the energetically most favorable adsorption site (denoted as C in Figure 4a) is located right above the sulfur anion. Detailed adsorption sites and adsorption energy are provided in the supplementary material. After unilateral hydrogen passivation, the central Ag layer shifts away from the adsorption side due to electrostatic repulsion, recovering the original bulk-like AgS4 tetrahedron with neighboring S ions.
Nonetheless, the magnetic ground state of AgCr2S4H remains A-AFM (e.g., in-plane FM). It is nontrivial, since the chemical valence of Cr has been restored to its bulk value (i.e., +3) after the hydrogen adsorption. The in-plane DS-AFM order observed in bulk has not been recovered, which is a little bit unexpected. As discussed previously, the in-plane magnetic pattern in bulk is structurally related, namely the Cr3+ ion spacing [22,35]. We compared the in-plane Cr-Cr spacing after unilateral H passivation with that of the bulk material. The Cr-Cr spacing after passivation is 3.55 Å larger than the bulk value (3.43/3.54 Å, this non-uniform spacing distribution is due to the DS-AFM order). According to GKA rules, the half-filled t2g orbitals of Cr3+ give rise to the AFM direct exchange which is sensitive to Cr-Cr spacing. In other words, large spacing weakens this AFM direct exchange, breaks the delicate balance and leads to the FM dominance, which well explains the FM behavior observed in the passivated AgCr2S4H material. Details of lattice constants are marked in Figure S4. This speculation is further proved by in-plane strain modulation. As shown in Figure 4c, the in-plane magnetic ground state is fragile and extremely sensitive to biaxial strain. The compressive strains can effectively shorten the in-plane Cr-Cr distance and enhance the direct AFM coupling, thus giving rise to the bulk-like DS order. On the contrary, the tensile strains will fasten the in-plane FM order (i.e., A-AFM).
In AgCrS2 bulk, the sandwiched Ag layer has been proved to be crucial to its structure, ferroelectricity, and ionic conductivity [17,20,33]. Here, in AgCr2S4 monolayer, Ag’s displacement to the central site restores the centrosymmetry and destroys the ferroelectricity. This displacement not only increases the CrS2 interlayer distance, but also weakens the binding between Ag ion and the upper/lower CrS2 layers (Ag-S bonds are halved from 4 to 2), which will certainly lead to the enhancement of ionic mobility as found in experiment [20].
To confirm this scenario, the possible displacement processes of Ag ion in AgCr2S4 as well as its H-passivated cases are simulated by the NEB method. The corresponding energy profiles are shown in Figure 5. Obviously, unilateral adsorption breaks the centro-symmetry and forces Ag to shift away from H, resulting in an asymmetric potential profile, which is consistent with our previous analysis. The simulation results of the AgCr2S4 monolayer and the bilaterally adsorbed AgCr2S4H2 are also presented in Figure 5 for comparison. In both AgCr2S2 and AgCr2S4H2, the sandwiched Ag ion tends to be located in the central site, with weak bonding between neighboring S ions. The energy barriers of AgCr2S2 and AgCr2S4H2 are 150 meV/Ag and 140 meV/Ag, respectively, making them much lower than in the case of AgCr2S4H (190 meV/Ag). For comparison, the energy barrier of AgCrS2 bulk was estimated to be 450 meV/Ag [17].
Based on the above analysis and numerical data, it is reasonable to conclude that the ionic conductivity of AgCrS2 can benefit from dimension reduction and may reach its peak in single-layer AgCr2S4 or its AgCr2S4H2.

4. Conclusions

In summary, the structural, magnetic, and electronic properties of bulk AgCrS2 and its single layer AgCr2S4 have been investigated. The in-plane DS pattern of bulk material has been confirmed, but its monolayer exhibits metallic in-plane FM behavior. The underlying mechanism is attributed to the hole-doping induced by exfoliation and the resulting change in Cr’s chemical valence. Moreover, the displacement of the sandwiched Ag ion towards the high-symmetry center was found, which eliminates the polarity and enhances the ionic conductivity. This structure-related superionic behavior is sensitive to surface adsorption. Specifically, it will be inhibited by unilateral adsorption, but will be recovered by bilateral adsorption. The present study may stimulate further experimental and theoretical research on AgCr2S4 and other 2D non-vdW materials.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/ma16083058/s1, Figure S1: In-plane structural parameters of phases α and β; Figure S2: MC simulations of the magnetic susceptibility and normalized magnetization of AgCr2S4 monolayer at different lattice sizes as a function of temperature; Figure S3: Hydrogen adsorption energy and possible adsorption sites of AgCr2S4H; Figure S4: Distance between the Cr-Cr of AgCrS2 and AgCr2S4H; Figure S5: Young’s modulus, shear modulus and Poisson’s ratio of AgCr2S4; Table S1: The lattice constants of AgCr2S4; Table S2: The elastic constants of AgCr2S4; Table S3: Mechanical parameters of AgCr2S4; Table S4: The energy of AgCr2S4H2 in different magnetic sequences [40,41,42,43,44,45].

Author Contributions

Conceptualization, S.D.; methodology, R.L., Y.W. and N.D.; validation, M.A. and S.D.; formal analysis, R.L., Y.W. and N.D.; resources, S.D. and M.A.; writing—original draft preparation, R.L.; writing—review and editing, M.A. and S.D.; visualization, R.L. and Y.W.; supervision, M.A., S.D. and N.D.; project administration, M.A. and S.D. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Science Foundation of China (Grant No. 12274069, 12274070).

Informed Consent Statement

Not applicable.

Data Availability Statement

Data supporting these findings are available from the corresponding authors upon request.

Acknowledgments

We thank the Big Data Center of Southeast University for providing the facility support on the numerical calculations.

Conflicts of Interest

The authors declare no conflict of interest.

Abbreviations

UeffEffective Hubbard parameter. In order to deal with the strong correlation of Cr3+, the Hubbard empirical parameter U is added using Dudarev’s approach, Ueff = UJ, where U and J are the on-site Coulomb interaction and the strength of the effective on-site exchange interaction, respectively.
SiThe normalized spin vector sitting on lattice site i.
J1 and J2The in-plane nearest neighbor and the next-nearest neighbor magnetic exchange coupling parameters.
kBThe Boltzmann constant.
MThe normalized magnetization.
χThe magnetic susceptibility.

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Figure 1. (a,b) Side view and top view of bulk AgCrS2. (c) Four in-plane magnetic configurations: ferromagnetic order (FM), stripe AFM (S-AFM), double-stripe order (DS-AFM), and zigzag AFM order (Z-AFM). Blue and red spheres indicate spin-up and spin-down Cr ions, respectively. The other ions are omitted for clarity. (d) The energy evolution of various magnetic orders as a function of Ueff. The DS state energy is taken as the reference value.
Figure 1. (a,b) Side view and top view of bulk AgCrS2. (c) Four in-plane magnetic configurations: ferromagnetic order (FM), stripe AFM (S-AFM), double-stripe order (DS-AFM), and zigzag AFM order (Z-AFM). Blue and red spheres indicate spin-up and spin-down Cr ions, respectively. The other ions are omitted for clarity. (d) The energy evolution of various magnetic orders as a function of Ueff. The DS state energy is taken as the reference value.
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Figure 2. (a,b) The top and side views of the AgCr2S4 asymmetric α phase (P3m1) and the centro-symmetric β phase (C2/m), respectively. The nearest neighbor interaction J1 and the next-nearest neighbor interaction J2 are denoted by the red dotted arrows in the right panel of (b). (c) The MC simulated magnetic susceptibility and normalized magnetization as a function of temperature for the AgCr2S4 monolayer.
Figure 2. (a,b) The top and side views of the AgCr2S4 asymmetric α phase (P3m1) and the centro-symmetric β phase (C2/m), respectively. The nearest neighbor interaction J1 and the next-nearest neighbor interaction J2 are denoted by the red dotted arrows in the right panel of (b). (c) The MC simulated magnetic susceptibility and normalized magnetization as a function of temperature for the AgCr2S4 monolayer.
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Figure 3. The density of states (DOS) of bulk AgCrS2 (upper panel) and monolayer AgCr2S4 (lower panel).
Figure 3. The density of states (DOS) of bulk AgCrS2 (upper panel) and monolayer AgCr2S4 (lower panel).
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Figure 4. (a) Possible adsorption sites for hydrogen. B, C, D denote the adsorption sites above the lower and upper S ions and Cr ion in the adjacent CrS2 layer, respectively. While, A and E are the adsorption sites located between CD and BC, respectively. (b) Side view of the ground structure of unilaterally passivated AgCr2S4H. (c) AgCr2S4H ground state phase diagram as a function of the lattice constant. Relative energy per unit cell is shown on the left axis. The energy of optimized free-standing structure with A-AFM ground state is taken for reference. Upper axis: the equivalent biaxial strain, defined as (aa0)/a0, where a0 and a are the in-plane lattice constants before and after stress application, respectively.
Figure 4. (a) Possible adsorption sites for hydrogen. B, C, D denote the adsorption sites above the lower and upper S ions and Cr ion in the adjacent CrS2 layer, respectively. While, A and E are the adsorption sites located between CD and BC, respectively. (b) Side view of the ground structure of unilaterally passivated AgCr2S4H. (c) AgCr2S4H ground state phase diagram as a function of the lattice constant. Relative energy per unit cell is shown on the left axis. The energy of optimized free-standing structure with A-AFM ground state is taken for reference. Upper axis: the equivalent biaxial strain, defined as (aa0)/a0, where a0 and a are the in-plane lattice constants before and after stress application, respectively.
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Figure 5. The switching paths of AgCr2S4H2 (grey), AgCr2S4H (blue), and AgCr2S4 (red) as simulated by NEB. Ag, Cr, S, and H ions are represented by gray, dark blue, yellow, and white balls in the illustrations, respectively.
Figure 5. The switching paths of AgCr2S4H2 (grey), AgCr2S4H (blue), and AgCr2S4 (red) as simulated by NEB. Ag, Cr, S, and H ions are represented by gray, dark blue, yellow, and white balls in the illustrations, respectively.
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Table 1. The energy differences of four in-plane collinear spin configurations. Interlayer coupling has also been considered, in which the AFM interlayer coupling is denoted by subscript 1 and the FM coupling is represented by subscript 2, respectively. The total energy of the ground state (β phase with A-AFM order) is taken as the reference value, in units of meV/Cr.
Table 1. The energy differences of four in-plane collinear spin configurations. Interlayer coupling has also been considered, in which the AFM interlayer coupling is denoted by subscript 1 and the FM coupling is represented by subscript 2, respectively. The total energy of the ground state (β phase with A-AFM order) is taken as the reference value, in units of meV/Cr.
A-AFMDS1-AFMZ1-AFMS1-AFMFMDS2-AFMZ2-AFMS2-AFM
α57.2568.4082.6288.2553.6566.4482.8223.39
β014.9911.6924.002.8813.6713.4022.41
Table 2. In-plane exchange parameters (meV/Cr) estimated from our DFT calculations.
Table 2. In-plane exchange parameters (meV/Cr) estimated from our DFT calculations.
J1J2KbKc
β phase−14.86−5.761.110.80
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Li, R.; Wang, Y.; Ding, N.; Dong, S.; An, M. Adsorption Tuning of Polarity and Magnetism in AgCr2S4 Monolayer. Materials 2023, 16, 3058. https://doi.org/10.3390/ma16083058

AMA Style

Li R, Wang Y, Ding N, Dong S, An M. Adsorption Tuning of Polarity and Magnetism in AgCr2S4 Monolayer. Materials. 2023; 16(8):3058. https://doi.org/10.3390/ma16083058

Chicago/Turabian Style

Li, Ranran, Yu Wang, Ning Ding, Shuai Dong, and Ming An. 2023. "Adsorption Tuning of Polarity and Magnetism in AgCr2S4 Monolayer" Materials 16, no. 8: 3058. https://doi.org/10.3390/ma16083058

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