lMatIndSym Function

public pure function lMatIndSym(a, b, c, i, j, k) result(index)

Arguments

Type IntentOptional Attributes Name
integer(kind=int64), intent(in), value :: a
integer(kind=int64), intent(in), value :: b
integer(kind=int64), intent(in), value :: c
integer(kind=int64), intent(in), value :: i
integer(kind=int64), intent(in), value :: j
integer(kind=int64), intent(in), value :: k

Return Value integer(kind=int64)


Contents

Source Code

lMatIndSym

Source Code

    pure function lMatIndSym(a, b, c, i, j, k) result(index)
        ! Indexing function implementing 48-fold symmetry:
        ! Symmetric with respect to permutation of pairs (a,i), (b,j) and (c,k) as well as
        ! with respect to exchange of a<->i, b<->j and c<->k
        ! Input: a,b,c - orbital indices of electrons
        !        i,j,k - orbital indices of holes
        ! Output: index - contiguous index I(a,b,c,i,j,k) with the aforementioned symmetry
        integer(int64), value, intent(in) :: a, b, c ! occupied orb indices
        integer(int64), value, intent(in) :: i, j, k ! unoccupied orb
        integer(int64) :: index

        integer(int64) :: ai, bj, ck

        ai = fuseIndex(a, i)
        bj = fuseIndex(b, j)
        ck = fuseIndex(c, k)

        ! sort the indices
        if (ai > bj) call swap(ai, bj)
        if (bj > ck) call swap(bj, ck)
        if (ai > bj) call swap(ai, bj)

        index = ai + bj * (bj - 1) / 2 + ck * (ck - 1) * (ck + 1) / 6
    end function lMatIndSym