Electronic, Mechanical and Elastic Anisotropy Properties of X-Diamondyne (X = Si, Ge)

The three-dimensional (3D) diamond-like semiconductor materials Si-diamondyne and Ge-diamondyne (also called SiC₄ and GeC₄) are studied utilizing density functional theory in this work, where the structural, elastic, electronic and mechanical anisotropy properties along with the minimum thermal conductivity are considered. SiC₄ and GeC₄ are semiconductor materials with direct band gaps and wide band gaps of 5.02 and 5.60 eV, respectively. The Debye temperatures of diamondyne, Si- and Ge-diamondyne are 422, 385 and 242 K, respectively, utilizing the empirical formula of the elastic modulus. Among these, Si-diamondyne has the largest mechanical anisotropy in the shear modulus and Young's modulus, and Diamond has the smallest mechanical anisotropy in the Young's modulus and shear modulus. The mechanical anisotropy in the Young's modulus and shear modulus of Si-diamondyne is more than three times that of diamond as determined by the characterization of the ratio of the maximum value to the minimum value. The minimum thermal conductivity values of Si- and Ge-diamondyne are 0.727 and 0.524 W cm^-1 K^-1, respectively, and thus, Si- and Ge-diamondyne may be used in the thermoelectric industry.