output_reference_space Subroutine

    subroutine output_reference_space(filename)
        use MPI_wrapper, only: root
        use util_mod, only: get_free_unit
        implicit none
        character(255), intent(in) :: filename
        integer :: iunit, i, ierr

        if (iProcIndex == root) then
            iunit = get_free_unit()
            open(iunit, file=filename, status='replace')
            ! write the references into the file
            do i = 1, nRefs
                write(iunit, *) ilutRefAdi(:, i)
            end do
            call neci_flush(iunit)
            close(iunit)
        end if
        call MPIBarrier(ierr)
    end subroutine output_reference_space