Universality of ionic criticality: Size- and charge-asymmetric electrolytes

Grand-canonical simulations designed to resolve critical universality classes are reported for z1 hard-core electrolyte models with diameter ratios λ=a+/a-6. For z=1 Ising-type behavior prevails. Unbiased estimates of Tc(λ) are within 1% of previous (biased) estimates but the critical densities are ∼5% lower. Ising character is also established for the 21 and 31 equisized models, along with critical amplitudes and improved Tc estimates. For z=3, however, strong finite-size effects reduce the confidence level although classical and O(n3) criticality are excluded.