Abstract
The phonon spectra of zinc-blende CuCl are studied as a function of pressure using density functional linear-response theory. A pressure-induced soft transverse-acoustic-phonon mode is identified. At 2.6 GPa, the TA phonon mode softens at the X point, initiating the phase transition from the zinc-blende structure CuCl-II to a cubic structure CuCl-IV. The previously proposed off-center displacement model and the Fermi resonance model for Raman anomalies are examined. This study suggests that the anomaly in the Raman spectrum results from Fermi resonance.
- Received 20 December 2002
DOI:https://doi.org/10.1103/PhysRevB.67.140301
©2003 American Physical Society