RECURSION METHOD SOLUTION OF COHERENT POTENTIAL APPROXIMATION EQUATIONS - APPLICATION TO SURFACE ALLOYS

摘要

We present a new method of solving the self-consistent field equations in the coherent-potential approximation (CPA). In our approach, the coherent potential and the Green function of the effective medium are represented as continued fractions. If is shown that, contrary to the standard CPA method, it is possible to define an energy-independent Hamiltonian, which acts in an augmented space, so that the recursion method can be directly used. The continued-fraction expansion of the Green function is taken until the desired accuracy is achieved and the density of states is calculated using the appropriate terminator. The method is directly applicable to an alloy surface and no further approximations other than the CPA are introduced. In particular, the method avoids the main difficulty of the standard CPA approach, i.e. the solution of coupled CPA equations for each energy point. First applications of the method to different alloy surfaces are presented. [References: 13]