Regular Article

The structural transition under densification and the relationship between structure and density of silica glass

¹ Department of Computational Physics, Hanoi University of Science and Technology, Hanoi, Viet Nam
² Simulation in Materials Science Research Group, Advanced Institute of Materials Science, Ton Duc Thang University, Ho Chi Minh City, Viet Nam
³ Faculty of Electrical and Electronics Engineering, Ton Duc Thang University, Ho Chi Minh City, Viet Nam
⁴ Institute of Applied Materials Science, Vietnam Academy of Science and Technology, No. 1A TL29 Str., Thanh Loc Ward, District 12, Ho Chi Minh City, Viet Nam
⁵ Thu Dau Mot University, Binh Duong Province, Viet Nam
⁶ Institute of Research and Development, Duy Tan University, Da Nang 550000, Viet Nam

^a e-mail: lethevinh@tdtu.edu.vn

Received: 8 March 2019
Received in final form: 2 June 2019
Published online: 26 August 2019

Abstract

The structure of silica glass (SiO₂) at different densities and at temperatures of 500 K is investigated by molecular dynamics simulation. Results reveal that at density of 3.317 g/cm³, the structure of silica glass mainly comprises two phases: SiO₄- and SiO₅-phases. With the increase of density, the structure tends to transform from SiO₄-phase into SiO₆-phase. At density of 3.582 g/cm³, the structure comprises three phases: SiO₄- , SiO₅-, and SiO₆-phases, however, the SiO₅- phase is dominant. At higher density (3.994 g/cm³), the structure mainly consists of two main phases: SiO₅- and SiO₆-phases. In the SiO₄-phase, the SiO₄ units mainly link to each other via corner-sharing bonds. In the SiO₅-phase, the SiO₅ units link to each other via both corner- and edge-sharing bonds. For SiO₆-phase, the SiO₆ units can link to each other via corner-, edge-, and face-sharing bonds. The SiO₄-, SiO₅-, and SiO₆-phases form SiO₄- SiO₅- and SiO₆-grains respectively and they are not distributed uniformly in model. This results in the polymorphism in the silica glass at high density.