Structural and elastic properties of antiperovskites XNBa3 (X=As, Sb) under pressure effect

First-principle calculations of structural, elastic and high pressure properties of antiperovskites XNBa3 (X=As, Sb) are performed, using the full-potential linear muffin-tin orbital (FP-LMTO) method. The local density approximation (LDA) is used for the exchange-correlation (XC) potential. Results are given for lattice constant, bulk modulus and its pressure derivatives. We have determined the elastic constants C11, C12 and C44 and their pressure dependence. We derived shear moduli, Young's modulus, Poisson's ratio and Lamé's constants for ideal polycrystalline XNBa3 aggregates. By analyzing the ratio of the bulk to shear moduli, we conclude that XNBa3 compounds are brittle in nature. We estimated the Debye temperature of XNBa3 from the average sound velocity. This is the first quantitative theoretical prediction of the elastic properties of AsNBa3 and SbNBa3 compounds, and it still awaits experimental confirmation.