Nullify all the face normal pionter
subroutine destroy_geometry()
!< Nullify all the face normal pionter
implicit none
call dmsg(1, 'geometry', 'destroy_geometry')
nullify(xnx)
nullify(xny)
nullify(xnz)
nullify(ynx)
nullify(yny)
nullify(ynz)
nullify(znx)
nullify(zny)
nullify(znz)
call deallocate_memory()
end subroutine destroy_geometry