PRIMITIVE = .TRUE.
or the PRIMITIVE_AXIS = ...
is specified, a primitive cell is defined. Just setting
PRIMITIVE = .TRUE.
, the subroutine create_primitive
suggests an example of primitive axes relative to a unit cell. Using
PRIMITIVE_AXIS = ...
, an arbitral primitive axes can be
used. This option is possibly used when a unit cell is not a primitive
cell, e.g., FCC and BCC cell.