Microstructure of lead silicate melt under compression: insight from computer simulation

The microstructure of lead silicate melt (Pb2SiO4) and its change under high pressure are investigated by molecular dynamics simulation. The models are constructed at temperature of 3000 K and in the 0–50 GPa pressure range. The microstructural correlate of pair radial distribution functions is clarified. Short range order (SRO) and intermediate range order (IRO) are investigated via topology analysis of SiOx units and SiOx-clusters. Microstructural analysis, cluster-analysis and visualization techniques are applied to clarify the characteristics of -Si-O- network structure. The local environment around Pb+2, Si+4 and O−2 ions, incorporation mechanism of Pb2+ cations into -Si-O- network, the microphase separation under compression have been clarified. Specially, the storage mechanism of hazardous metal ions (heavy metal ions in industrial and nuclear wastes) in silica-based multicomponent oxide systems is also discussed in detail

Structural organization, micro-phase separation and polyamorphism of liquid MgSiO

The structure, structural change and micro-phase separation in liquid MgSiO3 under pressure are studied by molecular dynamics simulation with pair-wise potentials. Models consisting of 5000 atoms are constructed at 3500 K in the 0–30 GPa pressure range. The structural organization and structural phase transition under compression as well as network topology of liquid MgSiO3 are clarified through analysis and visualization of molecular dynamics simulation data. The short-range structure, intermediate-range structure and the degree of polymerization as well as structural, compositional and dynamical heterogeneities are also discussed in detail

Study of diffusion and local structure of sodium-silicate liquid: the molecular dynamic simulation

A systematic analysis on sodium-silicate melt with various silica contents was carried out. The simulation revealed two diffusion mechanisms occurred in the melt: the bond-breaking and hopping between sites. The local structure was analyzed through T-simplexes. It was revealed that T-clusters have a non-spherical shape and represent the diffusion channel, in which Na atoms are dominant, but no any O atoms are located. The SiO2-poor melt acquires a long channel. In contrast, the SiO2-rich melt consists of unconnected short channels. The simulation also revealed the immobile and mobile regions which differ in local structure and constituent composition. We propose a new CL-function to characterizing the spatial distribution of different atom component. The spatial distribution of mobile and immobile atoms is found quite different. In particular, the immobile atoms are concentrated in high-density regions possessing very large density of immobile atoms. The spatial distribution of mobile atoms in contrast is more homogeneous