Solid-solid phase transitions and soft phonon modes in highly condensed Si

Journal Article · Sat Jun 15 04:00:00 EDT 1985 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.31.7819· OSTI ID:5790174

Chang, K J; Cohen, M L

The pseudopotential method is used to examine the structural transitions of Si from ..beta..-Sn to simple hexagonal (sh) to hexagonal close packed (hcp). The calculated transition pressures, transition volumes, and c/a ratios are in good agreement with the measured values. Furthermore, the phase-transition pressure from hexagonal close packed to face-centered cubic is predicted to be 1.2 Mbar. The phonon frequencies are also calculated with use of the frozen-phonon approximation for the ..beta..-Sn, sh, and hcp phases. For both the ..beta..-Sn and sh phases, pressure-sensitive soft phonon modes exist. These are the longitudinal optic mode at the Brillouin-zone center for ..beta..-Sn and the transverse acoustic mode at the Brillouin-zone boundary for sh in the (001) direction. These soft modes are most likely associated with the phase transformations from ..beta..-Sn to sh to hcp. The metallic sh phase has strong covalent interlayer bonding. This is opposite to the case for the graphite structure. The weak bonding in the hexagonal plane of the sh phase causes the soft transverse mode for this phase.

• Research Organization: Department of Physics, University of California, Berkeley, California 94720 and Materials and Molecular Research Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720
• OSTI ID: 5790174
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 31:12; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
656000 -- Condensed Matter Physics
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BRILLOUIN ZONES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY-LEVEL DENSITY
FCC LATTICES
HCP LATTICES
HEXAGONAL LATTICES
LATTICE VIBRATIONS
PHASE TRANSFORMATIONS
PHONONS
PHYSICAL PROPERTIES
QUASI PARTICLES
SEMIMETALS
SILICON
STABILITY
SUPERCONDUCTIVITY
VERY HIGH PRESSURE
ZONES