Theoretical Solid State Physics

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This grant supports a long-range, broad-based theoretical research program in condensed matter physics and computational materials science. The research projects cover the fields of semiconductors, metals, surfaces and interfaces, defects, superconductivity, materials under pressure, clusters, fullerene-based materials, nanotubes and other nanostructures, conjugated polymers, and many-electron effects in solids. The major objective is to use quantum theory to explain and predict the properties of materials. Emphasis is placed on using realistic models, close collaboration with experimentalists, investigations and suggestions for producing novel and useful materials, development of new theoretical approaches, and predictions related to electronic and structural properties of solids.Many new techniques based on quantum theory were developed in this research program to enable accurate calculations of real materials. In particular, the ab initio pseudopotential method and total energy techniques are applied within the density functional formalism to compute ground-state properties. Excited-state (spectroscopic) phenomena are investigated using a first-principle self-energy approach based on the GW approximation for quasiparticle excitations and an ab initio two-particle Green's function method based on the Bethe-Saltpeter equation for optical excitations. Other studies rely on variational and diffusion Monte Carlo approaches, molecular dynamics simulations, dielectric function methods, BCS theory, density functional perturbation theory, and extensions of standard many-body theory.Past successes include accurate predictions of properties and the existence of new materials, electronic structure calculations which allow band-gap engineering approaches to technology, and new theoretical approaches. The research program builds on this work and goes in several new directions. Specific projects include those related to understanding and predicting the properties of nanotubes, fullerenes, molecular junctions, and other nanostructures; electronic, vibrational and structural properties of materials at ambient and high pressure; mechanical properties, elastic stability and limit of strength of solids; electron-hole interaction and optical properties of solids, defects and polymers; quasiparticle excitations and electron correlations; and superconductivity and new formalisms. There is extensive involvement of graduate students and postdoctoral associates in this research.%%%This grant supports a long-range, broad-based theoretical research program in condensed matter physics and computational materials science. The research projects cover the fields of semiconductors, metals, surfaces and interfaces, defects, superconductivity, materials under pressure, clusters, fullerene-based materials, nanotubes and other nanostructures, conjugated polymers, and many-electron effects in solids. The major objective is to use quantum theory to explain and predict the properties of materials. Emphasis is placed on using realistic models, close collaboration with experimentalists, investigations and suggestions for producing novel and useful materials, development of new theoretical approaches, and predictions related to electronic and structural properties of solids. There is extensive involvement of graduate students and postdoctoral associates in this research.***