Extending multiple histogram reweighting to a continuous lattice spin system exhibiting a first order phase transition

We present extensive Monte Carlo simulations on a two-dimensional XY model with a modified form of interaction potential. Thermodynamic quantities other than energy, specific heat etc (such as magnetization, susceptibility, fourth order cumulant of magnetization) are obtained using multiple-histogram reweighting of the data obtained from the simulations. We employ an approach which eliminates the need to construct two-dimensional histograms. This approach makes judicious use of computer memory as well as CPU time. Lee-kosterlitz's method of finite size scaling for a first order transition and analysis using Binder's cumulant method allow us to make an accurate determination of the transition temperature.