Papers by Author: Soňa Charvátová

Abstract: This work aims to explore possible applications of the ab initio molecular dynamics (MD) in modeling of the soda-lime-silica (NCS) glass and melt doped with admixtures. Preparation of the basic glass (15.8 wt.% Na2O, 10.5 wt.% CaO, and 73.7 wt.% SiO2) by the MD simulation from scratch is described. The structure analysis of the NCS glass is presented in the form of total and partial radial distribution functions (RDF), coordination numbers, and fractions of Qn units. The reasonable first neighbor distances were obtained, even if a rather small basis set of electronic wavefunctions and softer pseudopotentials for atomic core regions were applied. All major discrepancies in the first neighbor distances can be easily explained, and the results can be improved if needed. The Qn distribution shows higher disproportionation of Q3 than NMR and Raman experimental data, however, it is lower than previous classical MD simulations.

Abstract: Alkali-silicate glass irradiated with electrons of the medium energy becomes to be fully depleted of alkali ions after some time. The chemical changes are expected to be accompanied with significant changes of glass structure. The changes in structure of 15K2O•85SiO2 glass were simulated by ab-initio MD. Experimental conditions were imitated by the following procedure. First, glass was prepared by the numerical cooling from the high-temperature melt. Second, alkali ions were removed. Third, silica structure was relaxed at temperatures 300 K and 1000 K. Structural changes are characterized in terms PP RDF’s and coordination numbers. It was found peroxide bonds were created from the dangling bonds, coming from non-bridging oxygen.