
Accession Number : ADA334648
Title : Theoretical Studies of Electronic, Vibrational, and Structural Properties of Solids under Pressure.
Descriptive Note : Final rept.,
Corporate Author : AIR FORCE RESEARCH LAB BOLLING AFB DC
Personal Author(s) : Lewis, Steven P.
PDF Url : ADA334648
Report Date : 1993
Pagination or Media Count : 127
Abstract : This dissertation describes firstprinciples quantum mechanical investigations of several realistic solidstate systems. The main goal of this research has been to understand and predict the electronic, vibrational, and structural properties of materials under pressure. Microscopic information on these properties is obtained within local density functional theory using ab initio pseudopotentials. This work focuses on three categories of materials: (1) Part I deals with the highpressure behavior of elemental systems from group IV of the Periodic Table. The pressuredependences of Ramanactive phonon modes of highpressure, metallic phases of silicon, germanium, and tin are studied within the frozenphonon approximation. In addition, the structural properties of a recently discovered orthorhombic phase of silicon are calculated. The aim of these two investigations is to understand and explain recent experimental results. A third investigation predicts the existence of an orthorhombic, highpressure phase of germanium. (2) Part II focuses on group V of the Periodic Table. The electronic and vibrational properties of elemental arsenic are studied with the aim of understanding the measured pressuredependences of the superconducting transition temperature and the normalstate resistance. In addition, several candidate atomic phases of solid nitrogen are studied to determine their structuralstability and electronic properties. (3) Finally, Part III considers the effect of varying the stoichiometry in compound systems. In particular, model calculations are performed to explore the GaAs system with the goal of motivating experimental studies. The electronic properties of several model GaAs systems with varying stoichiometry are studied.
Descriptors : *VIBRATION, *HIGH PRESSURE, *SOLIDS, *ELECTRONIC STATES, METALS, DENSITY, EXPERIMENTAL DATA, COMPUTATIONS, MODELS, ELECTROMAGNETIC PROPERTIES, QUANTUM THEORY, GALLIUM ARSENIDES, THESES, NITROGEN, PHASE, MICROSCOPY, TRANSITION TEMPERATURE, APPROXIMATION(MATHEMATICS), SILICON, TABLES(DATA), GROUP IV COMPOUNDS, GROUP V COMPOUNDS, TIN, PHONONS, GERMANIUM, ARSENIC, STOICHIOMETRY, SOLID STATE ELECTRONICS, SUPERCONDUCTIVITY.
Subject Categories : Quantum Theory and Relativity
Solid State Physics
Distribution Statement : APPROVED FOR PUBLIC RELEASE