Theoretical investigation of structural and elastic properties of Ag2SiS3 chalcogenide

Abstract

In this work, density functional theory was used to study the structural and elastic properties, cohesion energy, and formation energy of the Ag₂SiS₃ ternary chalcogenide compound. The calculations were performed using the norm-conserving and ultra-soft charge pseudo-potential in GGA and LDA approximations. The negativity of the measured value of cohesion and formation energy indicates the stability of the compound. At the E-Γ point, an indirect band gap with the sizes LDA + US = 1.17eV, GGA + US = 1.29 eV, and GGA + NC = 1.24 eV was obtained. Important characteristics of the elastic properties were studied, including anisotropy, bulk B, Young's modulus E, shear modulus G, minimum thermal conductivity (k_min), Cauchy pressure (P_C), Grüneisen parameter (γ), Poisson's ratio (ʋ), Debye temperature (θ_D), and melting temperature T_melt. From examining P_C, G/B, and ʋ, we found that the composition is ductile, and there are also ionic bonds between atoms. V was checked in (100), (010), and (001) directions; the value of V was different in these directions (V_l was greater than V_t in all directions), which indicates sound anisotropy. The θ_D value in this combination, LDA + US = 203.6 K, GGA + US = 217.54 K, and GGA-NC = 191.89 K, and the T_melt(±300K) value in LDA + US = 701.445 K, GGA + US = 644.85 K, and GGA-NC = 584.25 K, were obtained. The values obtained of K_min in the Clarke (Cahill) model have various amounts in different directions, and these values indicate the anisotropy of K_min. The values of K_min in the direction 100 in the Clark model are GGA-NC = 0.036 (W/mK), GGA-US = 0.042, and LDA-US = 0.043. After examining the properties of the Ag₂SiS₃ compound, we found that it is ductile, resistant, with good machinability, completely anisotropic, has strong atomic bonds, and is particularly stable. Given its properties, it is perfectly suitable for manufacturing and use in industry.