Theoretical calculation of the zero‐temperature isotherm and phase stability of silver up to 2 Gbar using the linear combinations of gaussian type orbitals method

Abstract

AbstractA systematic procedure has been developed for generating the static lattice zero temperature isotherm of a monatomic crystalline solid to arbitrarily high compressions using the linear combinations of Gaussian type orbitals‐fitting function electronic structure method. This procedure has been used to calculate the static‐lattice equation of state and phase stability of silver (Ag) up to 2 Gbar. The resulting isotherm is compared with previous density functional theory (DFT) calculations and experimental data at low pressures and with results from Thomas–Fermi–Dirac calculations at high pressures. The stabilities of three crystal structures (face centered cubic, fcc; body centered cubic, bcc; and hexagonal close packed, hcp) were determined from energy differences calculated up to 2 Gbar. The effects of relativity and DFT model selection were tested by repeating each calculation with and without relativistic corrections using two DFT models; the local density (LDA) and generalized gradient (GGA) approximations. The phase sequence for Ag is predicted to be fcc → hcp → fcc → hcp → bcc, although the second appearance of the hcp phase is questionable due to convergence issues. © 2012 Wiley Periodicals, Inc.