The models consisting of 19998 atoms were constructed under a wide range of pressure (0-20 GPa) and at 3500K temperature. Structural characteristics were clarified through the pair radial distribution function (PRDF), the distribution of SiOx coordination units and network structure. The result shows that these liquids consist of identical units SiO4, SiO5 and SiO6 and have common partial O―Si―O angle distribution. Furthermore, the major change in the diffusion mechanism under pressure is also considered and discussed. | VNU Journal of Science: Mathematics – Physics, Vol. 34, No. 4 (2018) 19-27 Molecular Dynamic Simulation of Large Model of Silica Liquid Nguyen Thi Thanh Ha1,*, Phan Quan1, Tran Van Hong2, Le Van Vinh1 1 Department of Computational Physics, Hanoi University of Science and Technology, Vietnam 2 Department of Physics, Thai Nguyen University of Education, Thai Nguyen, Vietnam Received 01 January 2018 Revised 30 February 2018; Accepted 20 March 2018 Abstract: We perform a molecular dynamics simulation to study the microstructure and dynamical properties in large silica model at liquid state. The models consisting of 19998 atoms were constructed under a wide range of pressure (0-20 GPa) and at 3500K temperature. Structural characteristics were clarified through the pair radial distribution function (PRDF), the distribution of SiO x coordination units and network structure. The result shows that these liquids consist of identical units SiO 4, SiO5 and SiO6 and have common partial O―Si―O angle distribution. Furthermore, the major change in the diffusion mechanism under pressure is also considered and discussed. Keywords: Molecular dynamics, structure, coordination units, diffusion, network structure . 1. Introduction Silica and silicate minerals (mixture of SiO2 and other metal oxides) play an important role in geosciences and technology. So, the complete knowledge of the structure and dynamical properties in silica and silicate under conditions of high pressure and temperature is quite necessary. The results of research studies will optimize the process of manufacturing new materials for intended use and controlling geological activities [1-4]. As we have known, the silicate glass- and meltstructures consists of SiO4 tetrahedra linking to each other form continuous random tetrahedral-network in three-dimensional space [5-7]. In pure silica glass and melt, each SiO4 tetrahedron connects to four other adjacent SiO4 tetrahedra via bridging-oxygen (BO). The addition of .
