Elastic and electronic properties of LiBSi2 under pressure from first principles

We investigate the structural, elastic and electronic properties of the tetragonal structure LiBSi2 under pressure from first principles in the frame of the density functional theory (DFT). Both local density approximation (LDA) and generalized gradient approximation (GGA) methods are used in our calculation. It is found that, the obtained lattice constants of LiBSi2 under zero pressure and zero temperature from GGA calculations are in better agreement with the available experimental data and other theoretical ones than those from LDA calculations. The hydrostatic (isotropic) pressure and non-hydrostatic (anisotropic) pressure dependences of the elastic constants Cij, bulk modulus B, shear modulus G, elastic anisotropy index AU, AB, AG, Young’s modulus E, Poisson’s ratio σ, aggregate acoustic velocities Vl and Vs, and Debye temperature ΘE of LiBSi2 are also presented. The pressure dependences of the elastic constants C11, C33, C12, and C13 vary largely under the effect of pressure when compared with the variations of C44 and C66. The calculated bulk modulus B from the elastic constants is 99 GPa, which is in agreement with the result obtained from the Vinet equation of state (105.01 GPa) and the result of Zeilinger et al. (103.7 GPa). In addition, GGA calculations give a band gap of 1.19 eV, indicating that the tetragonal structure LiBSi2 is a semiconductor, consistent with the experimental result.