The pressure effect on the structural, elastic, and mechanical properties of orthorhombic MgSiN2 from first-principles calculations

Abstract

Pressure effect on lattice parameters, elastic moduli, Poisson's ratio, Cauchy pressure, elastic anisotropy, and Vickers hardness of orthorhombic MgSiN2 by means of first-principles calculations based on density functional theory (DFT) by generalized gradient approximation (GGA) in the functional form by Perdew, Bruke, and Ernzerhof (PBE) of the exchange-correlation were presented. The structural properties, elastic moduli, B0/G, Poisson's ratio (ν) and Cauchy pressure under pressure up to 10 GPa were calculated. The optimized structural and ground state properties under ambient pressure were in agreement with the available experiments and other calculations. The orthorhombic MgSiN2 was mechanically stable under pressure up to 10 GPa by the elastic stability criteria investigation. Under pressure, the relationship of elasticity in length was C33 > C11 > C22, indicating that it is easier to compress along the b-axis than along the a-axis and c-axis, respectively. The calculated bulk modulus, shear modulus, Young's modulus and Poison's ratio index all increased with an increase in the pressure. The B0/G, Poisson's ratio (ν) and Cauchy pressure analyses implied that orthorhombic MgSiN2 was single crystal, and a critical pressure for brittle-to-ductile transition was found to be 2 GPa. The Cauchy pressure of {100} plane, {010} plane and {001} plane, Vickers hardness (Hv) and the shear anisotropy as a function of pressure were investigated from the calculation.