  An interatomic potential for the diamond and graphite phases of carbon has
been created using a neural-network (NN) representation of the ab initio
potential energy surface. The NN potential combines the accuracy of a
first-principle description of both phases with the efficiency of empirical
force fields and allows one to perform, for the first time, a molecular
dynamics study, of ab initio quality, of the thermodynamics of graphite-diamond
coexistence. Good agreement between the experimental and calculated coexistence
curves is achieved if nuclear quantum effects are included in the simulation.
