First-principles calculations of the structural, dynamical, and electronic properties of liquid MgO

Abstract

The structural, dynamical, and electronic properties of liquid MgO have been investigated over a wide range of pressure 0t o 240 GPa and temperature 3000– 10 000 K using first-principles molecular dynamics FPMD within the framework of density-functional theory and the pseudopotential approximation. Our results show that the liquid structure is highly sensitive to compression: the Mg-O coordination number increases from 5 at zero pressure to 7 at high pressure. The Gruneisen parameter and heat capacity are found to increase upon twofold compression by 40% and 20%, respectively. The dynamical behavior of the liquid phase is characterized by the diffusion coefficient, which is found to decrease with increasing pressure and to increase with increasing temperature in a way that can be accurately characterized by an Arrhenius relationship with activation energy and volume of 0.85 eV and 1.3 A 3 , respectively. The calculated electronic density of states show that the electronic structure of the liquid phase differs substantially from that of the crystalline phase: the liquid has no band gap and a density of states at the Fermi level increases with increasing volume and temperature.