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.