title: Order in dense hydrogen at low temperatures.
abstract: By increase in density, impelled by pressure, the electronic energy bands in dense hydrogen attain significant widths. Nevertheless, arguments can be advanced suggesting that a physically consistent description of the general consequences of this electronic structure can still be constructed from interacting but state-dependent multipoles. These reflect, in fact self-consistently, a disorder-induced localization of electron states partially manifesting the effects of proton dynamics; they retain very considerable spatial inhomogeneity (as they certainly do in the molecular limit). This description, which is valid provided that an overall energy gap has not closed, leads at a mean-field level to the expected quadrupolar coupling, but also for certain structures to the eventual emergence of dipolar terms and their coupling when a state of broken charge symmetry is developed. A simple Hamiltonian incorporating these basic features then leads to a high-density, low-temperature phase diagram that appears to be in substantial agreement with experiment. In particular, it accounts for the fact that whereas the phase I-II phase boundary has a significant isotope dependence, the phase II-III boundary has very little.
authors.affiliation: Department of Radiology, Stanford University School of Medicine, Stanford, CA 94305, USA.
authors.forename: B
authors.initials: B
authors.lastname: Edwards
authors.forename: N W
authors.initials: NW
authors.lastname: Ashcroft
mesh_terms: D003080:Cold Temperature; D003903:Deuterium / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry*; D007700:Kinetics; D011312:Pressure; D013816:Thermodynamics
chemical_list: D006859:Hydrogen; D003903:Deuterium