Prediction of first-order martensitic transitions in strained epitaxial films

Abstract

Coherent epitaxial growth allows us to produce strained crystalline films with structures that are unstable in the bulk. Thereby, the overlayer lattice parameters in the interface plane, (a, b), determine theminimum-energy out-of-plane lattice parameter, cmin (a, b).We showbymeans of density-functional total energy calculations that this dependence can be discontinuous and predict related firstorder phase transitions in strained tetragonal films of the elements V, Nb, Ru, La, Os, and Ir. The abrupt change of cmin can be exploited to switch properties specific to the overlayer material. This is demonstrated for the example of the superconducting critical temperature of a vanadium film which we predict to jump by 20% at a discontinuity of cmin.