OCCUPANCY-CORRELATION CORRECTIONS IN HOPPING

A theory of correlated hopping diffusion on lattices with site-exclusion interaction is presented. We develop a variational procedure to estimate the diffusion constant D. We derive a method of obtaining several sequences of decreasing upper bounds for D. The method is extensively discussed for the particular sequence that starts with the mean-field approximant D(MF). The first term of a second sequence D(MF) approximately is obtained by a suitable renormalization of the jump rates and is closer to D than D(MF). This modified mean-field approximation enables us to formulate an improved version of the Miller-Abrahams equivalence to a resistor network that includes correlation effects.