add MPI_finalize() following Martin & Philip suggestions;

code/DAMASK_spectral.f90

@@ -150,6 +150,7 @@ program DAMASK_spectral
    MPI_file_get_position, &
    MPI_file_write, &
    MPI_abort, &
+   MPI_finalize, &
    MPI_allreduce, &
    PETScFinalize
 
@@ -709,6 +710,11 @@ program DAMASK_spectral
 
  call PETScFinalize(ierr); CHKERRQ(ierr)
 
+ #ifdef _OPENMP
+ call MPI_finalize(i)
+ if (i /= 0_pInt) call IO_error(error_ID=894, el=i, ext_msg="Finalize()")
+ #endif
+
  if (notConvergedCounter > 0_pInt) call quit(3_pInt)                                                ! error if some are not converged
  call quit(0_pInt)                                                                                  ! no complains ;)