  We present theoretical calculations of the Raman and IR spectra, as well as
electronic properties at zero and finite temperature to elucidate the crystal
structure of phase III of solid molecular hydrogen. We find that anharmonic
finite temperature are particularly important and qualitatively influences the
main conclusions. While P6$_3$/m is the most likely candidate for phase III at
the nuclear ground state, at finite temperature the C2/c structure appears to
be more suitable.
