The crystal structures of solid hydrogen and solid deuterium in thin films

Reflection electron diffraction patterns obtained from thin films of solid hydrogen at approximately 5°K contain sharp rings from a face-centred cubic phase with a 0 = 5·29 ± 0·05 Å, and broader rings which are consistent within experimental error with the hexagonal close-packed structure reported by other workers. Reflection and transmission diffraction patterns obtained from solid deuterium at about 5°K and 7°K respectively contain sharp rings from a face-centred cubic phase with a 0 = 5·07 ± 0·05 Å at approximately 5°K. The atomic positions in the structures have not been determined. If it is assumed that there are eight atoms of hydrogen or deuterium per face-centred cubic unit cell, then the calculated densities for the solid elements are in accord with published data.