get_orb_from_kpoints Function

    function get_orb_from_kpoints(orbi, orbj, orba) result(orbb)
        ! write a cleaner implementation of this multiple used
        ! functionality.. because kPointToBasisFn to basisfunction
        ! promises more than it actually odes
        integer, intent(in) :: orbi, orbj, orba
        integer :: orbb

        integer :: ki(3), kj(3), ka(3), kb(3), ispn, spnb

        ki = G1(orbi)%k
        kj = G1(orbj)%k

        ! Given A, calculate B in the same way as before
        ka = G1(orba)%k
        kb = ki + kj - ka

        ispn = get_ispn([orbi, orbj])

        if (iSpn == 1) then
            spnb = 1
        else if (iSpn == 2) then
            ! w.d: bug found by peter jeszenski and confirmed by
            ! simon!
            ! i do not think this is so much more efficient than an
            ! additional if-statement which is way more clear!
            ! messed up alpa and beta spin here..
!             spnb = (-G1(orba)%Ms + 1)/2 + 1
            !       spnb = (G1(orba)%Ms)/2 + 1
            if (is_beta(orba)) then
                spnb = 2
            else
                spnb = 1
            end if
        else if (iSpn == 3) then
            spnb = 2
        end if

        ! damn.. for some reason this is different treated in the
        ! hubbard and UEG case..
        ! i turn off the thub flag in my new implementation, so this is
        ! never actually reached below.. i should change that

        if (t_k_space_hubbard) then
            orbb = lat%get_orb_from_k_vec(kb, spnb)
            return
        end if

        ! this now distinguishes between UEG and hubbard models.
        if (tHub) then
            call mompbcsym(kb, nbasismax)
        end if

        orbb = KPointToBasisFn(kb(1), kb(2), kb(3), spnb)

    end function get_orb_from_kpoints