(159f) The Putative Liquid-Liquid Transition Is a Liquid-Liquid Transition in Some Atomistic Models of Water
Here, we provide a resolution to this long-standing controversy by analyzing the hybrid Monte Carlo (HMC) code that Limmer and Chandler used to perform their free energy calculations for ST2. We show that the LC HMC code suffers from a fundamental design flaw that introduces significant sampling errors. These errors distort ST2âs equation of state and are easily detected using three rigorous statistical mechanics based consistency checks. When we correct the LC code, we recover the correct equation of state of ST2, in excellent agreement with two independent codes; the corrected code also satisfies the consistency checks. The corrected code gives clear evidence of two liquid phases in the free energy surface, while the uncorrected code reproduces the LC published results, which show a single liquid basin at conditions where several other studies have reported two liquid phases.