Molecular Dynamics Simulation of Amorphous SiO₂, B₂O₃, Na₂O–SiO₂, Na₂O–B₂O₃, and Na₂O–B₂O₃–SiO₂ Glasses with Variable\nCompositions and with Cs₂O and\nSrO Dopants

Abstract

Selection of suitable\nglass composition for vitrification of high-level\nradioactive wastes (HLWs) is one of the major challenges in nuclear\nwaste reprocessing. Atomic and molecular level understanding of various structural, thermodynamical, and dynamical\nproperties of a glass matrix can help in preliminary screening and\nthus reduce the dependency to some extent on tedious experimental\nprocedures. In that context, extensive molecular dynamics (MD) simulations\nhave been performed to calculate various microscopic properties of\nthe glass matrix. The present article demonstrates that the “Buckingham\npotential-included long-ranged Coulomb interaction” can be\nutilized to simulate the glasses of varied compositions. The proposed\nsimulation model has been validated for a wide range of glass compositions:\npure glass matrixSiO₂ and B₂O₃; binary glass mixturesSiO₂–B₂O₃, Na₂O–SiO₂, and Na₂O–B₂O₃; ternary glassNa₂O–SiO₂–B₂O₃; and also the Cs₂O- and SrO-doped matrix of sodium borosilicate.\nMost importantly, the MD results have been validated with those of\nin-house synthesized glasses. The effect of alkali addition on the\ndensity and network connectivity of the glass matrix has been explored.\nThe results capture well the boron anomalies for varied concentrations\nof network formers and network modifiers. The intermediate structural\nordering in glasses has been explored by calculating the partial and\ntotal structure factors. Further, the characteristic vibration density\nof states of constituent atoms in the glass matrix is determined.\nIn addition, the glass structures with the addition of dopant oxides\nCs₂O and SrO have been examined as they are known to be\nprime heat-generating agents in HLWs. The results establish the structure\nand dynamics of the doped glass matrix to be a complex nature of the\ndopant’s mass, concentration, charge, and ionic radius. The\npresent MD results might be of great academic and technological significance\nfor further studies in the field of vitrification and prediction of\neffects associated with the dopant’s nature and concentration.