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In this work, we use molecular dynamic (MD) simulation to study the structure transition and crystallization of amorphous silica (SiO2) under compression. The structural evolution of amorphous SiO2 is explained through radial distribution function, coordination number distribution, bond angle distribution and visualization. | VNU Journal of Science Mathematics Physics Vol. 36 No. 2 2020 13-22 Original Article Study of Structure Transition and Crystallization of Amorphous Silica under Compression Giap Thi Thuy Trang1 2 Pham Huu Kien1 1 Thai Nguyen University of Education 20 Luong Ngoc Quyen Thai Nguyen Vietnam 2 Ha Noi University of Science and Technology 1 Dai Co Viet Hanoi Vietnam Received 29 October 2019 Revised 13 December 2019 Accepted 25 December 2019 Abstract In this work we use molecular dynamic MD simulation to study the structure transition and crystallization of amorphous silica SiO2 under compression. The structural evolution of amorphous SiO2 is explained through radial distribution function coordination number distribution bond angle distribution and visualization. Simulation result shown that there is a structural transformation from tetrahedral to octahedral network through SiO 5 units. In the 5- 15 GPa pressure range structural transformation occurs powerfully and there are three structural phases corresponding to SiO4- SiO5- and SiO6- ones. At 15 GPa octahedral-network SiO6 is dominant. It is the first time we showed that when pressure is higher than 20 GPa octahedral- network of amorphous SiO2 has a tendency to transform to stishovite crystalline phase. Keywords Compression crystallization structural transformation phase amorphous. 1. Introduction Structural phase transformation under pressure of SiO2 is interesting that it is great importance in technology and geophysics 1-5 . The wide range distribution of Si-O-Si bond angle and bond length in silica gives rise to a rich variety of structures of phases in this system as functions of pressure and temperature. The laxity of the structure is the important condition of existence of the glass state. It accounts for the specific glass-forming properties of SiO2 and for the very low ability of forming crystalline of amorphous silica. The behavior of various high pressure silica phases has been investigated by both theory .
