Necessity of Large-Scaled and Non-Empirical Molecular Dynamics Simulation of Silicate Liquids at High Pressure

Abstract

The physical properties of silicate liquids show peculiar behaviors under pressure. Shear viscosities of acidic silicate liquids decrease with increasing pressure although that of basic silicate liquids increase. Moreover, the anomalies in compression curves also have been reported. These experimental results indicate that the silicate liquids have several types of characteristic structure in composition/pressure plane. The molecular dynamics simulation is an appropriate method for investigating response of static/dynamic properties of the silicate liquids vs. pressure and composition because it provides the trajectories of the all atoms in simulation cell. Moreover, the first-principles molecular dynamics simulation is more suitable method because the forces are calculated from electronic structure. It enables us to simulate the extreme situation, such as bond exchanging event in liquid, without empirical factor. However, the strong finite size effect does not allow the application of first-principles molecular dynamics simulations because of its heavy calculation cost, because the system composed of at least 10⁴ atoms is required in order to obtain the reliable physical properties. Consequently, the development of linear-scaling first-principles molecular dynamics simulation codes is necessary for the advance of theoretical study of silicate liquids.