Non-linear elastic behavior of hexagonal silicon carbide

Abstract

The full sets of non-vanishing second- and third-order elastic constants (SOEC and TOEC) in 2H-SiC have been determined by the method of homogeneous deformation with interactions extending upto fourth neighbors using the sublattice displacement to the first degree in strains. The effective SOEC are obtained in terms of SOEC and TOEC. The aggregate elastic moduli and its pressure dependence have been studied. In 2H-SiC, the value of , showing the compressibility along the ab-plane to be larger, reducing the system more anisotropic, which is corroborated in the pressure derivatives of SOEC. TOEC of the shear modes, like and have smaller values than their longitudinal counterparts like and , uantifying the effect of pressure on the longitudinal wave velocity to be greater. Absolute value of , predicting anisotropy along ab-plane to be more pronounced than c-axis. The pressure derivatives for the longitudinal moduli ( and ) are positive while the shear moduli ( and ) are negative, consistent with the pressure derivatives of the bulk modulus () and shear modulus () of polycrystalline 2H-SiC. The elastic shear softening predicts the B4 -to-B1 structural phase transformation in 2H-SiC.