High-pressure structural and electronic properties of carbon

Journal Article · Sat Aug 15 04:00:00 EDT 1987 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.36.3373· OSTI ID:6166884

Fahy, S; Louie, S G

The high-pressure properties of carbon in eight different structures are calculated using an ab initio pseudopotential local-orbital method. In particular, the structural properties of hexagonal diamond and variation of its fundamental band gap with pressure are calculated for the first time. The variation of the fundamental gap in hexagonal diamond is found to have the opposite sign to that in cubic diamond, although the cubic and hexagonal forms have almost identical structural properties. Among the structures examined, diamond is found to transform under hydrostatic pressure first to the fourfold coordinated bc-8 (or Si-III) structure. The bc-8 form is favored at pressures greater than 11.1 Mbar. This is a slightly lower transformation pressure than that recently calculated using the pseudopotential plane-wave method. The sixfold coordinated structures, simple cubic and US -tin, are found at low pressure to be kinetically unstable, transforming spontaneously, without an energy barrier, into the cubic diamond structure. This result suggests that sixfold coordination of liquid carbon will be unlikely to occur at moderate pressure and temperature. Similarly, sixfold coordination is not expected in carbon clusters. A method of fully utilizing crystal symmetry to reduce the amount of computation in evaluating two- and three-center integrals needed in the local-orbital method is developed for the present calculations.

• Research Organization: Department of Physics, University of California, Berkeley, California 94720 and Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6166884
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Journal Name: Phys. Rev. B: Condens. Matter; (United States) Vol. 36:6; ISSN PRBMD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
CARBON
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
CUBIC LATTICES
DENSITY
DIAMONDS
ELECTRONIC STRUCTURE
ELEMENTAL MINERALS
ELEMENTS
ENERGY GAP
FUNCTIONALS
FUNCTIONS
HEXAGONAL LATTICES
MINERALS
NONMETALS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
PRESSURE DEPENDENCE
SYMMETRY
VERY HIGH PRESSURE