Using the non-empirical Variational Induced Breathing (VIB) model, the thermal properties of periclase (MgO) under high pressures and temperatures are investigated using molecular dynamics, which includes all anharmonic effects. Equations of state for temperatures up to 3000K and pressures up to 310 GPa were calculated. Bulk modulus, thermal expansivity, Anderson-Gr¿neisen parameter, thermal pressure, Gr¿neisen parameter and their pressure and temperature dependencies are studied in order to better understand high pressure effects on thermal properties. The results agree very well with experiments and show that the thermal expansivity decreases with pressure up to about 100 GPa (&eegr;=0.73), and is almost pressure and temperature independent above this compression. It is also effected by anharmonicity at zero pressure and temperatures above 2500K. The thermal pressure changes very little with increasing pressures and temperatures, and the Gr¿neisen parameter is temperature independent and decreases slightly with pressure. ¿ American Geophysical Union 1995