Computer simulation study of hysteresis and free energy in the fcc Ising antiferromagnet

A method for estimating the entropy S from a Monte Carlo simulation, suggested previously by the author, is applied to the fcc Ising antiferromagnet with nearest-neighbor interactions and external magnetic field h. The estimated accuracy for S is 0.01% to 0.5%, which is, at least, 1 order of magnitude higher than has been obtained with thermodynamic integration by Binder. Comparison of the free-energy results for the coexisting ordered and disordered phases enables us to determine with high accuracy the first-order transition points and the discontinuities in the thermodynamic functions. For the residual ground-state entropies per spin S(0)/k/sub B/ at the critical fields h/sub c//J = 12 and 4, we obtain 0.249 89(2) [ = 0.360 51(3)ln2] and 0.239(1) [ = 0.345(1)ln2], respectively. The first result is significantly larger than the theoretical upper bound, sigma/sub u//sup prime/ = 0.2398 ( = 0.3460 ln2), conjectured by Hadjukovic and Milosevic. Our results are also significantly larger than Binder's result, approx.(1/3) ln2, obtained for both critical fields