DFT insights into Nb-based 211 MAX phase carbides: Nb₂AC (A = Ga, Ge, Tl, Zn, P, In, and Cd)

Abstract

Comparison of (a) stiffness constants and (b) elastic moduli of Nb2AC (A = Ga, Ge, Tl, Zn, P, In, Cd, and Al) MAX phases.

Structural stability and physical properties of MAX phases M2SX (M=Sc, Y, X=B, C, N) via first-principles calculations

“…The valence electronic configurations of the considered atoms are as follows: S-3s 2 3p 4 , B-2s 2 2p 1 , C-2s 2 2p 2 , N-2s 2 2p 3 , Sc-3p 6 4s 2 3d 1 , Y-4s 2 4p 6 5s 2 4d 1 . The cut-off energy was set to 600 eV, the total energy self-consistent convergence was set to 10 -6 eV u −1 n −1 it −1 cell with 0.02 eV/Å as the maximum force on each atom [47]. The Methfessel-Paxton smearing scheme was set to a width of 0.05 eV and a mesh size of 15 × 15 × 3 k-point sample was applied for Brillouin zone integration [48,49].…”

“…Table 1 shows calculated lattice constants a (Å) and c (Å), equilibrium volumes V (Å 3 /unit cell), internal parameter Z M , distortion of octahedral (O d ) and trigonal prism (P d ), molar mass M (g/mol), density ρ (×10 3 kg m −3 ), formation enthalpies ΔH (eV/atom) with other theoretical calculations [32,56,57]. The distortion of octahedral (O d ) and trigonal prism (P d ) are used to evaluate the distortions in 211-MAX phases using the following equation [47]:…”