Anharmonic Effects in the A 15 Compounds Induced by Sublattice Distortions

作者：Zhiwei Lu, Barry M. Klein · 发表于：Physical Review Letters · 年份：1997 · DOI：10.1103/physrevlett.79.1361 · 被引用次数：19 · 研究领域：High-pressure geophysics and materials、Physics of Superconductivity and Magnetism、Superconducting Materials and Applications

We demonstrate that elastic anomalies and lattice instabilities in the $A15$ compounds are describable in terms of first-principles local density approximation electronic structure calculations. We show that at $T\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ ${\mathrm{V}}_{3}\mathrm{Si}$, ${\mathrm{V}}_{3}\mathrm{Ge}$, and ${\mathrm{Nb}}_{3}\mathrm{Sn}$ are intrinsically unstable against shears with elastic moduli ${C}_{11}{\ensuremath{-}C}_{12}$ and ${C}_{44}$, and that the zone center phonons, ${\ensuremath{\gamma}}_{2}$ and ${\ensuremath{\gamma}}_{12}$, are either unstable or extremely soft. We demonstrate that sublattice relaxation (internal strain) effects are key to understanding the behavior of the $A15$ materials.