Structures of sodium aluminophosphate glasses from molecular dynamics simulations and experimental validation

N Marchin and M Watanabe and T Kobayashi and F Lodesani and S Urata and JC Du, JOURNAL OF THE AMERICAN CERAMIC SOCIETY, 109 (2025).

DOI: 10.1111/jace.70324

Modeling phosphate glasses presents significant challenges due to their intermediate-range structural complexity. This study focuses on developing a classical potential to model sodium aluminophosphate glasses, incorporating a three-body term to the existing effective two body potentials using molecular dynamics (MD) simulations with improved structural accuracy. The three-body term parameters were initially parameterized by fitting to density functional theory (DFT)-relaxed crystalline phosphates and subsequently refined by modeling binary and ternary phosphate glasses. The potential's performance was assessed by modeling six ternary sodium aluminophosphate glasses, three of which were prepared and characterized experimentally. Computational results were validated against Raman spectroscopy and 27Al and 31P magic-angle spinning (MAS) NMR experimental data and compared to those from previous studies. Incorporating the three-body potential was found to notably improved the Al coordination number, aligning more closely with NMR results, although there is still a gap between computational and experimental results, specifically for P-rich glasses. Additionally, the three-body term enhanced the regulation of intertetrahedral bond angles toward experimental values, with additional improvements in bond distances and Qn distribution. These findings demonstrate the capability of MD simulations in elucidating the complex atomic level structures of phosphate glasses. The results provided insinghts on the short and medium range structures of these glasses and highlight the importance of three-body interactions in modeling phosphate and aluminophosphate glasses.

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