Structural, elastic, and thermodynamic properties of hexagonal molybdenum nitrides under high pressure from first principles

The structural and elastic properties of hexagonal molybdenum nitrides (delta-MoN) at high pressure were investigated through the first-principles calculation using local density approximation and generalized gradient approximation within the plane-wave pseudopotential density functional theory. The obtained equilibrium structure and mechanical properties are in excellent agreement with other experimental and theoretical results. Then we compared the elastic modulus of delta-MoN. By the elastic stability criteria, it is predicted that delta-MoN is stable in our calculations (0-100 GPa). The calculated B/G ratios indicate that delta(1)-MoN (space group of P-6m2, No. 187) possesses brittle nature within 100 GPa, but delta(3)-MoN (space group of P63mc, No. 186) possesses brittle nature below 46.7 GPa and it begins to prone to ductility when the pressure increases to 46.7 GPa. Through the quasi-harmonic Debye model, we also investigated the thermodynamic properties of delta-MoN. (C) 2015 Elsevier B.V. All rights reserved.