  We present results predicting experimentally measurable structural quantities
from molecular dynamics studies of hydrogen. In doing this, we propose a
paradigm shift for experimentalists -- that the predictions from such
calculations should be seen as the most likely hypotheses. Specifically, the
experimental results should be aiming to distinguish between the candidate
low-energy structures, rather than aiming to solve the simplest structure
consistent with the data. We show that the room temperature X-ray diffraction
patterns for hydrogen phases I, III, IV and V are very similar, with only small
peaks denoting symmetry-breaking from the hcp Phase I. Because they incorporate
atomic displacements the XRD patterns implied by molecular dynamics
calculations are very different from those arising from the static minimum
enthalpy structures found by structure searching. Simulations also show that
within Phase I the molecular becomes increasingly confined to the basal plane
and suggest the possibility of an unusual critical point terminating the Phase
I-III boundary line.
