Phys. Rev. B Abstract
Abstract
We present the results of first-principles molecular-dynamics simulations of mol
ten silicates,
based on the density functional formalism.
In particular, the structural properties
of a calcium
aluminosilicate CaO-Al2O3-SiO2
melt are compared
to those of a silica melt. The local structures of the two melts are in
good agreement with the experimental understanding of these systems.
In the calcium aluminosilicate melt, the number of
non-bridging oxygens found is in excess of the number obtained from a simple
stoichiometric prediction. In addition, the aluminum avoidance principle,
which states that links between AlO4
tetrahedra are absent or rare,
is found to be violated. Defects such as 2-fold rings and 5-fold coordinated
silicon atoms are found in comparable proportions
in both liquids.
However, in the calcium aluminosilicate melt,
a larger proportion of oxygen atoms are 3-fold coordinated. In addition,
5-fold coordinated aluminum atoms are observed.
Finally evidence of creation and anihilation
of non-bridging oxygens is observed, with these oxygens being mostly
connected to Si tetrahedra.