Programme

P.77 -- Poster, VCTP-44

Date: Thursday, 1 August 2019

Time: 08:30 - 10:00

Dynamics heterogeneity and diffusion mechanism in sodium-silicate melts. Molecular dynamics simulation

Nguyen Thi Thanh Ha, Nguyen Thu Nhan

Hanoi University of Science and Technology

In the present study we use molecular dynamics simulation to investigate sodium-silicate melts with various compositions at 1873 K and ambient pressure. The microstructure and diffusion have been studied with help of simplex and cluster of simplexes. The simulation shows that the simplex contains up to 6 Na and the radius of simplexes varies from 1.4 to 4.5 Å. In the SiO2-rich melt the majority of simplexes are void-simplexes and simplexes containing 1 Na. As the SiO2 content of the melt decreases, the fraction of simplexes having 2, 3 and 4 Na monotonously increases. We find that the temporal number density of Na around Si and BO is significantly smaller than that around NBO and FO. The static structure is heterogeneous and comprises Na-poor and Na-rich regions occupied by Si-O subnets and S-clusters, respectively. The simulation also reveals "pockets for sodium" where NF atoms (O and Si) having large number density of Na gather. The structure comprises rigid micro-regions and the dynamics is spatially heterogeneous. The diffusion pathways for sodium consist of simplex-regions of solid-like NBO, FO and liquid type O. Moreover, Na atoms pass more intensively through such pathways than the simplex-regions of solid-like BO and Si.

Presenter: Nguyen Thi Thanh Ha