Abstract
Different noble gases (He, Ne, and Ar) containing densified silica liquids and glasses are investigated from molecular dynamics simulations at different system densities using a dedicated force field. The results for pure silica are first compared to reference potentials prior to an investigation of the thermodynamic diagram, the diffusivity, and the structure under different (T, P) conditions. It is found that the equation of state and the diffusivity are weakly sensitive to the nature of the incorporated noble gas, leading to a similar trend with density for all systems. The network structure is weakly altered by the presence of the gas, and pressure induced structural changes are those usually found for amorphous and liquid silica, i.e., Si coordination increase, tetrahedral to octahedral conversion of the base geometry, and collapse of large rings under pressure. Ne- and Ar-based systems display an increased structuration, however, as preferential distances appear in gas-gas correlations at large densities in both the liquid and amorphous states. Finally, we focus on the conditions of heterogeneity that are driven by the formation of noble gas bubbles, and these appear for a threshold density ρc that is observed for all systems.
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