Computer Simulation of the Polymerizable Oxide Melts Nanostructure Using the Descriptor-Graph Model

Abstract

The paper describes the method for modeling of nanostructure polymerizable multicomponent oxide melts, which can be used for systems of type Me2O-SiO2 (Me = monovalent cation), with the results of a molecular dynamics simulation as input. The models of the short-range and medium-range orders taking into account dual behavior of monovalent alkali metal cations able to form stable groups with oxygen atoms are built. The melt structure is described with help of heterogeneous descriptors which are constructed using the polymer models and molecular dynamics results. The model is a heterogeneous graph which is built with gradually increasing of mapping levels (from selection heterogeneous graph vertices associated with individual particles, to forming connected components of vertices corresponding polyanionic complexes and rings in the melt. Quantitative calculations of the structure associated characteristics are carried out using the distribution function of graph vertices. We have modeled nanostructure and studied polymerization processes in the system SiO2-Na2O in the range of five compositions by the above method. In particular, we calculated the radial and angular distribution, the distribution of the coordination numbers, the bond lengths, the mole portions of different types of oxygen atoms, the complex anions in the model system taking into account sodium ions, the proportion of flat rings in polyanionic complexes, as well as the average connection factor. The obtained results give a satisfactory agreement with the characteristics in the range having experimental data. A number of results the structure modeling has a scientific novelty and practical significance.