Structure of Molten CaSiO3: Neutron Diffraction Isotope Substitution with Aerodynamic Levitation and Molecular Dynamics Study

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Abstract
We have performed neutron diffraction isotopic substitution experiments on aerodynamically levitated droplets of CaSiO3, to directly extract intermediate and local structural information on the Ca environment. The results show a substantial broadening of the first Ca–O peak in the pair distribution function of the melt compared to the glass, which comprises primarily of 6- and 7-fold coordinated Ca-polyhedra. The broadening can be explained by a redistribution of Ca–O bond lengths, especially toward longer distances in the liquid. The first order neutron difference function provides a test of recent molecular dynamics simulations and supports the MD model which contains short chains or channels of edge shared Ca-octahedra in the liquid state. It is suggested that the polymerization of Ca-polyhedra is responsible for the fragile viscosity behavior of the melt and the glass forming ability in CaSiO3.

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