Slow dynamics attributed to topological frustration

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On the basis of a new theoretical concept of topological frustration physical mechanism of pressure-induced amorphization was investigated conducting both molecular dynamics simulations and synchrotron x-ray diffraction experiments. A molecular crystal tin tetraiodide was chosen as a target sample, which has been known as a pressure-induced glass former. The very mechanism of the amorphization was elucidated to be due to molecular dissociation. Appearance of the effects of topological frustration on the local structure as well as the macroscopic thermodynamic features in the low-pressure regime is discussed on the basis of the results hitherto obtained, which were theoretically re-examined focusing on the intermolecular interaction. A possible source of modification of the latter is a short-ranged octupole-octupole interaction, which may be a dominant contribution under high pressures. Finally, the phenomena of molecular dissociation occurred in SnI_4 is interpreted in terms of topological frustration.