Numerical simulation of electrical conductivity in microscopically inhomogeneous materials

The electrical transport properties of some microscopically inhomogeneous disordered materials were simulated by numerical calculations of the conductivity of cubic resistor networks with correlated bonds, both above and below the percolation threshold. The major effect of increasingly strong correlation among the metallic bonds is to shift the percolation threshold to lower values of the allowed metallic volume fraction, resulting in $C^{*}=0.15\mathrm{}\pm 0.02$ for the continuous-percolation limit. The numerical data were utilized for a quantitative fit of the electrical-conductivity data of metal-ammonia solutions and of alkali-tungsten bronzes, which undergo a continuous metal-nonmetal transition via the inhomogeneous transport regime.