  A new phase V of hydrogen was recently claimed in experiments above 325 GPa
and 300 K. Due to the extremely small sample size at such record pressures the
measurements were limited to Raman spectroscopy. The experimental data on
increase of pressure shows decreasing Raman activity and darkening of the
sample, which suggests band-gap closure and impending molecular dissociation,
but no definite conclusions could be reached. Furthermore, the available data
is insufficient to determine the structure of phase V, which remains unknown.
Introducing saddle-point $ab$ $initio$ random structure searching (sp-AIRSS),
we find several new structural candidates of hydrogen which could describe the
observed properties of phase V. We investigate hydrogen metallisation in the
proposed candidate structures, and demonstrate that smaller band gaps are
associated with longer bond lengths. We conclude that phase V is a stepping
stone towards metallisation.
