Dynamical coherent-potential approximation and tight-binding linear muffintin orbital approach to correlated electron system

Dynamical coherent-potential approximation (CPA) to correlated electrons has been extended to a system with realistic Hamiltonian which consists of the first-principles tight-binding linear muffintin orbital (LMTO) hands and intraatomic Coulomb interactions. Thermodynamic potential and self-consistent equations for Green function are obtained on the basis of the functional integral method and the harmonic approximation which neglects the mode-mode couplings between the dynamical potentials with different frequency. Numerical calculations have been performed for Fe and Ni within the second-order dynamical corrections to the static approximation. The band narrowing of the quasiparticle states and the 6 eV satellite are obtained for Ni at finite temperatures. The theory leads to the Curie-Weiss law for both Fe and Ni. Calculated effective Bohr magneton numbers are 3.0 mu(B) for Fe and 1.2 mu(B) tor Ni, explaining the experimental data. But calculated Curie temperatures are 2020 K for Fe and 1260 K for Ni, being still overestimated by a factor of two its compared with the experimental ones. Dynamical effects on electronic and magnetic properties are discussed by comparing with those in the static approximations.