The additional network-modifying cation oxide breaking up this network by the generation of nonbridging O atoms and it has a slight effect on the topology of SiOx and OSiy units. Moreover, the diffusion of network- former atom in sodium-silicate melt is anomaly and diffusion coefficient for sodium atom is much larger than for oxygen or silicon atom. The simulation proves two diffusion mechanisms of the network-former atoms and modifier atoms. | VNU Journal of Science Mathematics Physics Vol. 36 No. 2 2020 37-46 Original Article The Microstructural Transformation and Dynamical Properties in Sodium-silicate Molecular Dynamics Simulation Nguyen Thi Thanh Ha1 Tran Thuy Duong1 Nguyen Hoai Anh2 1 Hanoi University of Science and Technology No. 1 Dai Co Viet Hanoi Viet Nam 2 Nguyen Hue High School Quang Trung Ha Dong Hanoi Viet Nam Received 19 March 2020 Revised 03 May 2020 Accepted 04 June 2020 Abstract Molecular dynamics simulation of sodium-silicate has been carried out to investigate the microstructural transformation and diffusion mechanism. The microstructure of sodium silicate is studied by the pair radial distribution function distribution of SiO x x 4 5 6 OSiy y 2 3 basic unit bond angle distribution. The simulation results show that the structure of sodium silicate occurs the transformation from a tetrahedral structure to an octahedral structure under pressure. The additional network-modifying cation oxide breaking up this network by the generation of non- bridging O atoms and it has a slight effect on the topology of SiOx and OSiy units. Moreover the diffusion of network- former atom in sodium-silicate melt is anomaly and diffusion coefficient for sodium atom is much larger than for oxygen or silicon atom. The simulation proves two diffusion mechanisms of the network-former atoms and modifier atoms. Keywords Molecular dynamics microstructural transformation mechanism diffusion sodium-silicate. 1. Introduction The structural transformation in multi-component oxide glasses has received special attention over the past decades 1-3 . The process of structural transformation effects mechanical- physical- and chemical-properties. The structural transformation was observed by X-ray Raman scattering infrared spectroscopy data X-ray diffraction 4-6 . Namely the influence of pressure on the structural transformation of silica materials that is the typical network-forming oxide with corner-sharing SiO4 .