Compressibility exponent γ from ising to mean-field theories

The critical exponent γ is estimated from the high-temperature series for the compressibility of the lattice gas on a simple-cubic lattice with variable first-, second-, third-, and fourth-neighbor interactions. The standard Padé-approximant and ratio-of-coefficients methods are employed in the analysis. The results show that (i) the exponent changes with (certain) variations in the energy parameters of the model, and (ii) the exponent decreases monotonically as more-distant-neighbor interactions are taken into account in molecular-field-like potentials.