Simulating the phosphorus fluid–liquid phase transition up to the critical point

Abstract

We report a Car–Parrinello molecular dynamics study of the temperature dependence ofthe fluid–liquid phase transition in phosphorous, involving the transformation of amolecular fluid phase into a network-like phase. We employed density-functional theory(DFT) with a gradient-corrected functional (B-LYP) to describe the electronic structureand interatomic interactions and performed simulations in a constant pressureensemble. We spanned a temperature interval ranging from 2500 to 3500 K. Withincreasing temperature, we found that the structural conversion from the molecularP4 fluid into the network liquid occurs at decreasing pressures, consistent with experimentalobservations. At lower temperatures the transition is characterized by a suddenincrease of density in the sample. The magnitude of the density change decreaseswith increasing temperature and vanishes at 3500 K. In the temperature range3100–3500 K we found signals of near- and super-criticality. We identified localstructural changes that serve as seeds triggering the overall structural transition.