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Updated: Jan 28, 2026

An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Band gap closure, incommensurability and molecular dissociation of dense chlorine
Philip Dalladay-Simpson1, Jack Binns2, Miriam Peña-Alvarez3
1Center for High Pressure Science Technology Advanced Research, 1690 Cailun Road, Shanghai, 201203, China. philip.dalladay-simpson@hpstar.ac.cn.
Abstract:
Diatomic elemental solids are highly compressible due to the weak interactions between molecules. However, as the density increases the intra- and intermolecular distances become comparable, leading to a range of phenomena, such as structural transformation, molecular dissociation, amorphization, and metallisation. Here we report, following the crystallization of chlorine at 1.15(30) GPa into an ordered orthorhombic structure (oC8), the existence of a mixed-molecular structure (mC8, 130(10)-241(10) GPa) and the concomitant observation of a continuous band gap closure, indicative of a transformation into a metallic molecular form around 200(10) GPa. The onset of dissociation of chlorine is identified by the observation of the incommensurate structure (i-oF4) above 200(10) GPa, before finally adopting a monatomic form (oI2) above 256(10) GPa.
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