The structural, elastic, electronic, optical, and thermodynamic properties of B2X3 (X = S, Se) in different structural phases

In this study, the structural, mechanical, electronic, optical, and thermodynamic properties of the monoclinic (P21/c) and tetragonal (I41/a) structures of B2X3 (X = S, Se) were investigated using density functional theory. The generalized gradient approximation was employed in the calculations. The calculated lattice parameter values are in agreement with the experimental values. Mechanical properties were calculated using the stressstrain method. Based on the low elastic modulus values, it was concluded that the investigated structures are not hard materials. Anisotropic mechanical calculations revealed that the P21/c structure exhibits high anisotropy, whereas the I41/a structure shows low anisotropy. Electronic structure analysis revealed that the B2S3 and B2Se3 compounds exhibit semiconducting properties. The real and imaginary parts of the dielectric function, as well as other optical functions, L, n, k, and R, were calculated and interpreted for the P21/c and I41/a structures. Thermodynamic properties confirm that the P21/c and I41/a structures are thermally stable; the free energy decreases continuously with increasing temperature, while entropy increases.