Negative thermal expansion coefficient and isostructural transition in fcc cesium

作者：N. E. Christensen, Dave Boers, J. L. van Velsen, D. L. Novikov · 发表于：Physical review. B, Condensed matter · 年份：2000 · DOI：10.1103/physrevb.61.r3764 · 被引用次数：27 · 研究领域：High-pressure geophysics and materials、Rare-earth and actinide compounds、Thermodynamic and Structural Properties of Metals and Alloys

The equation of state of solid cesium in the face-centered-cubic (fcc) structure is examined theoretically by means of ab initio calculations. The electronic energy is calculated within density-functional theory, whereas vibrational contributions to energy and entropy are calculated within the quasiharmonic approximation. The thermal expansion coefficient is predicted to be negative for pressures above 3.5 GPa and up to the end of the stability range of the fcc phase for all T. The fcc phase becomes unstable around 4.3 GPa, where a transverse phonon mode with a wave vector along (110) becomes soft. According to the calculations an isostructural transition does not occur.