Phase diagram of a two-dimensional system with anomalous liquid   properties
  Using Monte Carlo simulation techniques, we calculate the phase diagram for a square shoulder-square well potential in two dimensions that has been previously shown to exhibit liquid anomalies consistent with a metastable liquid-liquid critical point. We consider the liquid, gas and five crystal phases, and find that all the melting lines are first order, despite a small range of metastability. One melting line exhibits a temperature maximum, as well as a pressure maximum that implies inverse melting over a small range in pressure. 
Ahmad M. Almudallal, Sergey V. Buldyrev and Ivan Saika-Voivod
cond-mat.soft cond-mat.stat-mech