Journal of the Physical Society of Japan
Extension of the Method of Exact Diagonalization of Quantum Spin Models to Finite Face Centred Cubic Lattices and Estimation of theT=0Properties of theS=1/2XYFerromagnet on the Infinite fcc Lattice
G.E. Stewart, Donald D. Betts, James Flynn
Abstract
First we introduce the upper triangular lattice form method that permits one to derive easily the complete set of finite lattices of any given number, N , of vertices for any regular infinite lattice in any number of dimensions, and we use it to obtain all finite fcc lattices of N <28. We compute the ground state energy, magnetization and spin-spin correlations of the spin one-half X Y ferromagnet on each of these lattices. Extrapolation of these data to infinite N yields T =0 estimates of the properties mentioned. Our estimates agree to a few tenths of a percent with spin wave, series expansion and variational estimates.