A. Cordelli et al., AUGMENTED SPACE FORMALISM AND RENORMALIZATION FOR GROUND AND EXCITED-STATES OF MAGNETIC SYSTEMS, Zeitschrift fur Physik. B, Condensed matter, 97(4), 1995, pp. 543-547
The augmented space formalism has been used so far for the study of di
sordered crystals. We stress here that the topological structure of th
e augmented space of a binary alloy is formally equivalent to the set
of configurations of an Ising system. In particular in both cases a ve
ry useful binary representation for labelling the vectors of the space
can be done. Starting from this observation we have developed a very
efficient description of the Ising hamiltonian, and we have shown that
it can be succesfully applied both in the direct diagonalization appr
oach and in conjunction with the renormalization scheme. Within this l
ast case we have proposed a generalization of the techniques commonly
used in the literature, obtaining very good results.