LCAO approach to the coherent potential approximation: electronic structure of substitutionally disordered CuNi alloys

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Abstract
An LCAO approach to the density functional first-principles CPA theory of substitutionally disordered alloys is presented. The formal difference from the traditional tight-binding CPA consists of the explicit appearance of the overlap matrix in the CPA equations. More important, the first-principles self-consistent electronic structure theory may be directly implemented into the scheme. The theory is applied to paramagnetic CuNi alloys. Green function calculations involving Brillouin zone integrations are performed with the help of an improved complex energy k-space integration method. Details of the numerical procedures for the evaluation of the density of states (DOS) and the Fermi energy are discussed. Within the LCAO-CPA formalism an explicit formula for the integrated DOS is derived. Numerical results were obtained for the DOS, state-projected DOS and self-energies, Bloch spectral function and the Fermi surface. Good agreement is found with both previous KKR-CPA calculations and experimental data.