Ab-initio DFT Calculations on Elastic Coefficients, (001) Surface Energy, Stability Limit of Pure Metals and Separation Energy of Bimetal Interface

Abstract

Ab-initio density functional theory (DFT) calculations on the elastic coefficients at no-load equilibrium, (001) surface energy and stability limit under the [001] static tension are implemented for eight fcc, four bcc and four hcp metals. The elastic coefficients and surface energy are compared with DFT database of Materials Project, Zhou’s EAM potential, and experimental data available. The stability limit is evaluated with the eigenvalues of the elastic stiffness matrix, B_ij = Δ_σi/Δ_εj . Here Δ_σi and Δ_εj are the change in the stress and strain in Voigt notation. Most elements show instability for the eigenvalues of η_Born(= B₁₁ − B₁₂) or η_spinodal of the 3x3 partial matrix of B_ij . Pt and W show instability for shear component B₄₄ while Fe does for B₆₆. Then the separation energy of bimetal interface for 120 combinations of these 16 metal elements are estimated from the energy deference of adhered/separated interface in a supercell of stacked unit lattices.