  Conventional molecular dynamics simulation has been used to determine melting
temperature of highly compressed classical molecular hydrogen in a wide range
of pressures and temperatures using non-empirical atom-atom potentials
approximation. It is shown that the raise of melting temperature with
increasing pressure becomes more and more smooth and at megabar pressures its
slope goes negative. We discuss the reasons of this turnover and analyze
connection of this effect with the parameters of chemical bonding in H2.
