Liquid-liquid phase transformation in carbon

A first order phase transition is found in liquid carbon using atomistic si mulation methods and Brenner's bond order potential. The phase line is term inated by a critical point at 8801 K and 10.56 GPa and by a triple point on the graphite melting line at 5133 K and 1.88 GPa. The phase change is asso ciated with density and structural changes. The low-density liquid is predo minantly sp bonded with little sp(3) character. The high-density liquid is mostly sp3 bonded with little sp character. This is the first nonempirical evidence of a liquid-liquid transition between thermodynamically stable flu ids. [S0031-9007(99)08961-9].