COMPOSITION AND TEMPERATURE EFFECTS ON SHORT AND MEDIUM-RANGE ORDER IN LITHIUM SILICATE GLASSES: A MOLECULAR DYNAMICS STUDY

Abstract

Molecular dynamics (MD) simulations were employed to examine the composition- and temperature-dependent structure of Li₂O.m SiO₂ glasses with m = 1, 2, and 4, denoted LS1, LS2, and LS4, over 300–973 K. The simulated models reproduce the principal peak positions and overall features of available neutron structure-factor and pair-distribution data, providing a basis for comparative structural analysis. The internal geometry of the SiO₄ tetrahedra is comparatively stable, with Si–O distances of approximately 1.55–1.60 Å and Si–O coordination close to four. Network connectivity changes strongly with composition through the balance between bridging oxygens (BOs) and non-bridging oxygens (NBOs): increasing SiO₂ raises the average O–Si coordination from about 1.33 in LS1 to 1.78 in LS4 and decreases NBO/T from approximately 2.0 to 0.5, while Li retains a broad oxygen-coordination environment dominated by four- and fivefold states. Temperature produces only minor changes in characteristic bond distances and NBO/T. Quantitative first sharp diffraction peak (FSDP) parameters show a weak and composition-dependent thermal response, whereas increasing SiO₂ content produces a more pronounced and narrower neutron-weighted FSDP. These results identify composition as the dominant control on network connectivity and the neutron-weighted medium-range structural signature, while temperature causes comparatively modest changes without substantially reconstructing the local SiO₄ framework or the average BO/NBO topology. The principal contribution is the direct, internally consistent separation of composition- and temperature-induced responses using the same interaction potential, preparation protocol, and structural descriptors.