Title

Effective action approach to first-principles many-body calculations

Date of Completion

January 1997

Keywords

Physics, Condensed Matter

Degree

Ph.D.

Abstract

First principles calculations of many-body systems represent an important tool for investigating the properties of real materials. This work describes the effective action formalism as a rigorous theoretical framework for the development for such calculations. Similar to density-functional theory the effective action formalism reduces the analysis of an interacting many-body system to a self-consistent solution of single-particle equations. This formalism is free of the limitations of the conventional density-functional theory. It is equally applicable for the analysis of ground as well as excited state properties. The formalism is illustrated by constructing density and spin-density based description of nonrelativistic many-electron system. This leads to an explicit diagrammatic expressions for the exchange-correlation functional and provides a systematic density based analysis of one-electron propagators and many-body excitation energies. Numerical results for the excitation energies for several closed shell atoms are presented. ^