Development of bromine-related potentials for molecular dynamics simulations of the oxyhalide photo-thermo-refractive glass

YJ Zhang and JP Yan and ZY Zhu and FM Wang and L Deng and DB He and JC Du and LL Hu, CERAMICS INTERNATIONAL, 49, 26794-26802 (2023).

DOI: 10.1016/j.ceramint.2023.05.216

The oxyhalide photo-thermo-refractive (PTR) glass has found various applications in optical devices. However, due to its complex compositions, researches on the structures and structure-property relationship of this kind of materials is still limited. In this work, we applied molecular dynamics (MD) simulations to investigate the structure of the classic PTR glass (excluding Ce, Ag, Sb, and Sn). A set of bromine-related potential parameters has been developed and tested by comparing the simulated crystal structures with those from experiments or ab initio calculations. The PTR glass has then been simulated by using MD simulations with the newly developed potentials. The structure information of the PTR glass, such as the pair distribution function, bond angle distribution, coordination number, and two-dimensional distributions of elements, have been calculated and compared with available experimental data from literature. In addition, the growth of the fluorine/bromine-rich regions in the PTR glass after heat treatment has also been investigated. It is found that the bromine prefers to stay around the fluorine-rich regions and form the phase boundary between the fluorine-rich phase and the oxygen-rich glass matrix. And the presence of sodium ions in the fluorine/bromine-rich regions increase the aggregation tendency of these regions thus lead to the growth of the region size. The results show that the newly developed bromine/fluorine- related potential parameters can describe the PTR glass structures thus provide a new method to help design and improve new applications.

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