Theoretical studies of hard materials, novel conductors, and high-pressure phases of solids

Miscellaneous · Tue Jan 01 00:00:00 EST 1991

OSTI ID:7041782

Liu, A Y.M.

The behavior of electrons and ions in a variety of condensed matter systems is studied using ab initio pseudopotentials and local density functional theory. The goal is to understand and predict the electronic and structural properties of these solids from first principles. Specific applications include: (1) An investigation of the behavior of the group IV elements, Si and Pb, under pressure. The fcc structural phase of Si, which is observed at pressures near 100 GPa, is predicted to be a free-electron-like metal with a superconducting transition temperature of about 2 K. The solid-solid and solid-liquid phase transitions in compressed Pb are also studied. Comparisons are made with recent experimental results. (2) A study of the electronic bonding in protypical metallic and covalent hard solids. The objective is to predict new hard materials. The bonding in the intermetallic compound WC is found to be a complex mixture of ionic, covalent, and metallic components. For covalent systems, the investigation indicates that partially tetrahedral C-N solids are good candidates for new low-compressibility materials. (3) Investigations of some light solids composed of elements in the first row of the periodic table. Several models for the atomic arrangement in the recently synthesized compound, BC[sub 2]N, are considered. A relation between the symmetry of the BC[sub 2]N monolayer and its conducting properties is found. The structural properties of a novel three dimensional all-sp[sup 2] structure for C are also examined. Lastly, a calculation of the electron-phonon coupling parameter for Li is used to rule out the suggestion that the observed lack of superconductivity in Li is due to a weak electron-phonon interaction in the low temperature 9R phase.

• Research Organization: California Univ., Berkeley, CA (United States)
• OSTI ID: 7041782
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
36 MATERIALS SCIENCE
ELECTRIC CONDUCTORS
ELECTRICAL PROPERTIES
PHASE STUDIES
SOLIDS
BORON NITRIDES
CARBON NITRIDES
ELECTRODYNAMICS
ELECTRON-PHONON COUPLING
ELECTRONIC STRUCTURE
LEAD
PHASE TRANSFORMATIONS
SILICON
SOLID STATE PHYSICS
STRUCTURAL CHEMICAL ANALYSIS
THEORETICAL DATA
BORON COMPOUNDS
CARBON COMPOUNDS
COUPLING
DATA
ELEMENTS
INFORMATION
METALS
NITRIDES
NITROGEN COMPOUNDS
NUMERICAL DATA
PHYSICAL PROPERTIES
PHYSICS
PNICTIDES
SEMIMETALS
665000* - Physics of Condensed Matter- (1992-)
360606 - Other Materials- Physical Properties- (1992-)
360104 - Metals & Alloys- Physical Properties
360602 - Other Materials- Structure & Phase Studies