Structure and diffusion in amorphous aluminium silicate: A molecular dynamics computer simulation
arXiv:cond-mat/0305227 · doi:10.1063/1.1630562
Abstract
The amorphous aluminium silicate (Al2O3)2(SiO2) [AS2] is investigated by means of large scale molecular dynamics computer simulations. We consider fully equilibrated melts in the temperature range 6100K >= T >= 2300K as well as glass configurations that were obtained from cooling runs from T=2300K to 300K with a cooling rate of about 10^12K/s. Already at temperatures as high as 4000K, most of the Al and Si atoms are four-fold coordinated by oxygen atoms. Thus, the structure of AS2 is that of a disordered tetrahedral network. The packing of AlO4 tetrahedra is very different from that of SiO4 tetrahedra in that Al is involved with a relatively high probability in small-membered rings and in triclusters in which an O atom is surrounded by four cations. We find as typical configurations two-membered rings with two Al atoms in which the shared O atoms form a tricluster. On larger length scales, the system shows a microphase separation in which the Al-rich network structure percolates through the SiO2 network. The latter structure gives rise to a prepeak in the static structure factor at a wavenumber q=0.5Å^{-1}. The comparison of experimental X-ray data with the results from the simulation shows a good agreement for the structure function. The diffusion dynamics in AS2 is found to be much faster than in SiO2. We show that the self-diffusion constants for O and Al are very similar and that they are by a factor of 2-3 larger than the one for Si.
30 pages of Latex, 13 figures
References in corpus (15)
- Cooling rate effects in amorphous Silica: A Computer Simulation Study
- Molecular dynamics calculation of the thermal conductivity of vitreous silica
- Static and Dynamic Properties of a Viscous Silica Melt Molecular Dynamics Computer Simulations
- Molecular structural order and anomalies in liquid silica
- Computer simulations of liquid silica: equation of state and liquid-liquid phase transition
- Structure and Dynamics of amorphous Silica Surfaces
- Channel diffusion of sodium in a silicate glass
- High Frequency Dynamics of Amorphous Silica
- The dynamics of sodium in sodium disilicate: Channel relaxation and sodium diffusion
- Structural properties of molten silicates from ab initio molecular-dynamics simulations: comparison between CaO-AlO-SiO and SiO
- The relaxation dynamics of a viscous silica melt: II The intermediate scattering functions
- Structural and electronic properties of the sodium tetrasilicate glass NaSiO from classical and ab initio molecular-dynamics simulations
- Transport phenomena and microscopic structure in partially miscible binary fluids: A simulation study of the symmetrical Lennard-Jones mixture
- Classical and ab initio molecular dynamic simulation of an amorphous silica surface
- Dynamics of SiO glasses