CalcCell Subroutine

    SUBROUTINE CalcCell
        !Detemines the cell size for a given cutoff and lattice type

        integer :: ii, jj, kk, EE
        logical :: under_cutoff

        if (real_lattice_type == "sc" .OR. dimen < 3) then
            NMAXX = int(sqrt(orbEcutoff)) + 1
            if (dimen > 1) NMAXY = int(sqrt(orbEcutoff)) + 1
            if (dimen > 2) NMAXZ = int(sqrt(orbEcutoff)) + 1
        else if (real_lattice_type == "bcc" .or. real_lattice_type == "fcc") then
            ! calculate needed cell size
            ii = 0  ! ii is always positiv. jj varies from -ii to ii, kk from -|jj| to |jj|
            under_cutoff = .true.
            do while (ii <= int(orbEcutoff) .and. under_cutoff) !until  no E < cutoff was found
                under_cutoff = .false.
                jj = -ii
                do while (abs(jj) <= abs(ii) .and. .not. under_cutoff) !until E < cutoff is found or jj =ii
                    kk = -abs(jj)
                    do while (abs(kk) <= abs(jj) .and. .not. under_cutoff)!until E < cutoff is found or kk=jj
                        !calculate unscaled energy for ii, jj, kk
                        EE = (k_lattice_vectors(1, 1) * ii + k_lattice_vectors(2, 1) * jj + k_lattice_vectors(3, 1) * kk)**2
                        EE = EE + (k_lattice_vectors(1, 2) * ii + k_lattice_vectors(2, 2) * jj + k_lattice_vectors(3, 2) * kk)**2
                        EE = EE + (k_lattice_vectors(1, 3) * ii + k_lattice_vectors(2, 3) * jj + k_lattice_vectors(3, 3) * kk)**2
                        if (EE <= orbEcutoff) under_cutoff = .true.
                        kk = kk + 1
                    end do
                    jj = jj + 1
                end do
                ii = ii + 1
            end do
            NMAXX = ii!-1
            NMAXY = ii!-1
            NMAXZ = ii!-1
        end if ! lattice type
        return

    END SUBROUTINE CalcCell