  MgO is an abundant mineral in the rocky mantle of terrestrial planets, but
its melting behaviors remain enigmatic. Here we introduce a simple theoretical
model to investigate the B1-liquid transition of MgO up to 370 GPa. Vibrational
free energies of B1-MgO are fully computed by the moment recurrence technique
in quantum statistical physics. On that basis, we associate the melting
temperature with the isothermal bulk modulus via the work-heat equivalence
principle. This strategy allows us to quantitatively explain recent
experimental data. Our numerical analyses would yield insights into planetary
dynamics and evolution.
