Tetragonal states from epitaxial strain on metal films

TL;DR

This paper uses first-principles electronic theory to analyze how isotropic pseudomorphic epitaxial strain affects the tetragonal phases of various metals, identifying stable and unstable states and providing detailed lattice and elastic properties.

Contribution

It introduces a first-principles calculation of epitaxial strain effects on tetragonal metal phases, revealing multiple equilibrium states and their stability regions.

Findings

Each metal has two stable tetragonal phases separated by an instability region.

Lattice constants and energies for these phases are tabulated.

Elastic constants for each phase are provided.

Abstract

The tetragonal states produced by isotropic pseudomorphic epitaxial strain in the (001) plane on a tetragonal phase of a crystal are calculated for V, Ti, Rb, Li, K, Sr from first-principles electronic theory. It is shown that each metal has two tetragonal phases corresponding to minima of the total energy with respect to tetragonal deformations, hence are equilibrium phases, and that the equilibrium phases are separated by a region of inherent instability. The equilibrium phase for any strained tetragonal state can thus be uniquely identified. Lattice constants and relative energies of the two phases and the saddle point between them are tabulated, as well as the tetragonal elastic constants of each phase.