Construction of the First-Principles Non-Local Theory of Electron Correlations and Its Application to the Quasi-Two Dimensional Iron Compounds

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In order to describe the properties of correlated electron systems quantitatively, we have extended our theories of electron correlations towards the first-principles and nonlocal theory. At T=0, we formulated the first-principles nonlocal theory on the basis of the self-consistent projection operator method (SCPM) and the LDA+U Hamiltonian. In addition, we developed the momentum-dependent local-ansatz variational theory to calculate the static correlation functions which appear in the 1st-principles SCPM. At finite temperatures, we formulated the nonlocal dynamical CPA which takes into account the long-range inter-site correlations on the basis of the off-diagonal effective medium and the incremental cluster expansion. Furthermorewe developed the first-principles molecular dynamics method which describes the nonlocal inter-site correlations within the high-temperature approximation.