  Melting of MgO was studied using a multicanonical ensemble method combined
with a first-principles calculation. This approach has been successively
performed by using a rather simple functional form for a model inter-atomic
potential that is determined from first-principles and a novel approximation
treating auxiliary degrees of freedom, such as electron thermal excitations,
within a multicanonical ensemble method. Although a rather simple model
potential was used, this approach could distinguish differences due to the
exchange-correlation potential used in the first-principles calculations. The
pressure dependence of the melting point, latent heat, and volume change during
melting were studied. The obtained dependence was similar to that reported by
Alfe which differs from experimental results. This dependence did not change
even with the PBEsol exchange-correlation potential.
