This variable selects in which units I/O of XYZ files should be
performed.
Options:
bohr_units:
The XYZ will be assumed to be in Bohr atomic units.
angstrom_units:
XYZ files will be assumed to be always in Angstrom,
independently of the units used by Octopus. This ensures
compatibility with most programs, that assume XYZ files have
coordinates in Angstrom.