Abstract
The phonon instabilities of cesium related to its pressure-induced phase transitions are studied using the density-functional perturbation theory. It is found that at low pressure, both the bcc and fcc Cs are dynamically stable, but fcc is thermodynamically metastable. The high-pressure phase transitions of Cs from bcc to and from to are related to the phonon instabilities of the long-wavelength acoustic modes resulted from the negative tetragonal shear elastic constant During the phase transition, all the phonon modes become soft, making it the most striking feature of this isostructural phase transition.
- Received 27 January 2000
DOI:https://doi.org/10.1103/PhysRevB.62.3624
©2000 American Physical Society