Phonon instabilities in high-pressure bcc-fcc and the isostructural fcc-fcc phase transitions of Cs

Journal Article · Tue Aug 01 04:00:00 EDT 2000 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.62.3624· OSTI ID:20217229

Xie, Jianjun ^[1]; Chen, S P ^[1]; Tse, John S ^[2]; Klug, Dennis D ^[2]; Li, Zhiqiang ^[2]; Uehara, Kentaro ^[2]; Wang, L G ^[3]

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1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2. Steacie Institute for Molecular Science, National Research Council of Canada, Ottawa, Ontario, Canada K1A 0R6 (Canada)
3. Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin-Dahlem, (Germany)

The phonon instabilities of cesium related to its pressure-induced bcc-to-fcc{sup (1)}-to-fcc{sup (2)} 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 fcc{sup (1)} and from fcc{sup (1)} to fcc{sup (2)} are related to the phonon instabilities of the long-wavelength acoustic modes resulted from the negative tetragonal shear elastic constant C{sup '}=(1/2)(C{sub 11}-C{sub 12}). During the fcc{sup (1)}-to-fcc{sup (2)} phase transition, all the phonon modes become soft, making it the most striking feature of this isostructural phase transition. (c) 2000 The American Physical Society.

• OSTI ID: 20217229
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 6 Vol. 62; ISSN 1098-0121
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BCC LATTICES
CESIUM
CRYSTAL-PHASE TRANSFORMATIONS
EXPERIMENTAL DATA
FCC LATTICES
FUNCTIONAL ANALYSIS
HIGH PRESSURE
PERTURBATION THEORY
PHONONS
PRESSURE DEPENDENCE
THEORETICAL DATA