Structure-composition trends in multicomponent borosilicate-based glasses deduced from molecular dynamics simulations...

Area of Science:

• Materials Science
• Computational Chemistry
• Solid State Chemistry

Background:

• Understanding glass structure-property relationships is crucial for designing advanced materials.
• Existing models often lack transferability across diverse glass compositions.
• Bioactive glasses require precise structural control for optimal bone-bonding properties.

Purpose of the Study:

• To investigate composition-structure trends in a wide range of glass systems using molecular dynamics (MD) simulations.
• To develop and validate new interatomic potentials for accurate simulation of borate and phosphate glasses.
• To elucidate the structural roles of network formers and modifiers (Na+, Ca2+) in complex glass networks.

Main Methods:

• Comprehensive MD simulations of 25 glasses across four systems: Na2O-B2O3, Na2O-B2O3-SiO2, Na2O-CaO-SiO2-P2O5, and Na2O-CaO-B2O3-SiO2-P2O5.
• Development and application of new B-O and P-O potential parameters within the polarizable shell-model framework.
• Validation against experimental data for BO3/BO4 and orthophosphate fractions, and analysis of coordination environments, bond lengths/angles, and cation-network interactions.

Main Results:

• Simulations accurately reproduced experimental data on borate and phosphate speciation.
• Local coordination environments ({BO3, BO4, SiO4, PO4}) were independent of co-existing network formers.
• Glass network polymerization (bridging vs. non-bridging oxygens) primarily governed structural trends.
• Na+ and Ca2+ cations predominantly associated with SiO4/BO3 groups, with specific interactions in NBO-rich or B-rich networks.

Conclusions:

• The developed MD approach provides high accuracy and transferability for diverse glass compositions.
• Glass structure is mainly dictated by network polymerization and the speciation of network formers.
• Cation-network interactions are complex, with Na+/Ca2+ roles varying based on glass composition and NBO content, influencing charge compensation mechanisms.