Polyatomic molecular liquids under extreme compression: facts, models, and a few predictions

Abstract

Early work by Siringo, Pucci and March (Phys. Rev. B, 37, 2491 (1988)) studied solid I₂ under high pressure at T = 0. Their conclusion was that insulating crystalline I₂ at low pressures eventually transformed into a molecular metal. This has subsequently been confirmed experimentally. Later studies by Weir et al. (Phys. Rev. Lett., 76, 1860 (1996)) on solid H₂ under pressure point in the same direction, though in the solid phase the metallic state has still not been achieved at low temperatures. However, in the liquid phase, an insulating metallic transition has been proposed, as in solid iodine, again on the basis of experimental high-pressure studies. Here, attention is shifted to some polyatomic molecules, such as the 10-electron series H₂O, NH₃ and CH₄. Particular attention is focused on the measured Hugoniots of the polyatomic molecular liquids.

Keywords:

• polyatomic molecular liquids
• Hugoniots
• molecular dissociation

Acknowledgements

This letter was brought to completion during a visit of GGNA and NHM to the Department of Physics, University of Antwerp. Thanks are due to Professors C. van Alsenoy and D. Lamoen for their warm hospitality. NHM was partially supported by FWO-Vlaanderen under Project No. G.0425.05.