SetupUMat2d_dense Subroutine

    subroutine SetupUMat2d_dense(nBasis)
        integer, intent(in) :: nBasis
        integer :: nBI, i, j
        integer :: ierr
        character(*), parameter :: t_r = 'SetupUMat2d_dense'

        nBI = numBasisIndices(nBasis)
        ! allocate the storage
        if (.not. associated(UMat2D)) then
            allocate(UMat2D(nBI, nBI), stat=ierr)
            call LogMemAlloc('UMat2D', nBI**2, 8 * HElement_t_size, t_r, tagUMat2D, ierr)
        end if

        ! and fill in the array
        do i = 1, nBI
            do j = 1, nBI
                if (i == j) then
                    UMat2d(i, i) = get_umat_el(i, i, i, i)
                else
                    ! similarly the integrals <ij|ij> in UMat2D
                    UMat2D(j, i) = get_umat_el(i, j, i, j)
                    UMat2D(i, j) = get_umat_el(i, j, j, i)
                end if
            end do
        end do
    end subroutine SetupUMat2d_dense