8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

Fri 911:10-14:00P1.29Ab initio molecular dynamics study of pressure-inducedmetallization of covalent liquidSatoshi Ohmura 1 and Fuyuki Shimojo 11 Kumamoto University, Kurokami 2-39-1, 860-8555, Kumamoto, JapanCovalent liquids under high pressure have been intensively studied because they are closely relatedwith igneous processes in the Earth. For a number of covalent liquids, the viscosity drops significantlywith increasing pressure. This anomalous behavior of the viscosity originates from the factthat the covalent interactions between atoms become weak under pressure. The other interestingphenomenon is the pressure-induced metallization of covalent liquids. It is well known that thehigh pressure leads to the metallization of liquid selenium and liquid arsenic chalcogenides whichare typical covalent liquids. However, the relationship between the structural changes and thepressure-induced metallization is still unknown. In order to clarify the microscopic mechanism ofthe metallization of covalent liquids, we investigate the structural and bonding properties of liquidSe and liquid AsS under pressure using ab initio molecular dynamics simulations. An importantfinding is that, even after metallization, there is a microscopic covalent-like interaction betweenatoms, which results in a peculiar behavior in both liquids. For liquid Se, after metallization, thereis a characteristic first coordination shell in which each atom interacts with neighboring atomsthrough covalent like bonding. As a result, the radial distribution function of liquid Se under pressurehas a peculiar shape in the sense that there are no clear peaks like in a dilute gas. For liquidAsS, the distance between As and S becomes longer with increasing pressure even after metallization.In addition, the diffusion coefficients have local maximum in the pressure range of themetallic state. These behaviors are shown in the covalent liquids which do not have the metallicstate up to quite high pressure, such as liquid B 2 O 3 and liquid SiO 2 . We discuss the effects of themicroscopic covalent-like interaction on the macroscopic properties in the metal state of Se andAsS under pressure.29