Instability Phenomenon in a Crystal under an External Force and a New Criterion for Its Occurrence

Abstract

General properties of instability phenomena in crystals caused by external forces are studied by the continuum approximation of the self-consistent Einstein model. A new criterion for an occurrence of the instability is proposed on the basis of the response of lattice vibration to a change of the stress. A method to classify the instability phenomena is briefly shown by utilizing a simple example.