Absence of metallization in solid molecular hydrogen
S. Azadi, Th. D. Kühne
Institute of Physical Chemistry and Center for Computational Sciences,
Johannes Gutenberg University Mainz, 55128 Mainz, Germany
Abstract
Being the simplest element with just one electron and proton the
electronic structure of a single Hydrogen atom is known exactly. However,
this does not hold for the complex interplay between them in a solid and in
particular not at high pressure that is known to alter the crystal as well as
the electronic structure and eventually causes solid hydrogen to become
metallic. In spite of intense research efforts the experimental realization
of metallic hydrogen, as well as the theoretical determination of the crystal
structure has remained elusive. Here we present a computational study
showing that the distorted hexagonal P63/m structure is the most likely
candidate for Phase III of solid hydrogen. We find that the pairing
structure is very persistent and insulating over the whole pressure range,
which suggests that metallization due to dissociation may precede eventual
bandgap closure. Due to the fact that this not only resolve one of major
disagreement between theory and experiment, but also excludes the conjectured
existence of phonon-driven superconductivity in solid molecular hydrogen, our
results involve a complete revision of the zero-temperature phase diagram of
Phase III.