CreateSpinInvBRR Subroutine

    SUBROUTINE CreateSpinInvBRR()

        ! Create an SpinInvBRR containing spin orbitals,
        ! unlike 'createInvBRR' which only has spatial orbitals.
        ! This is used for the FixCASshift option in establishing whether or not
        ! a determinant is in the complete active space.
        ! In:
        !    BRR(i)=j: orbital i is the j-th lowest in energy.
        !    nBasis: size of basis
        ! SpinInvBRR is the inverse of BRR.  SpinInvBRR(j)=i: the j-th lowest energy
        ! orbital corresponds to the i-th orbital in the original basis.
        ! i.e the position in SpinInvBRR now corresponds to the orbital number and
        ! the value to the relative energy of this orbital.

        IMPLICIT NONE
        INTEGER :: I, t, ierr
        CHARACTER(len=*), PARAMETER :: this_routine = 'CreateSpinInvBrr'

        IF (ALLOCATED(SpinInvBRR)) return

        allocate(SpinInvBRR(NBASIS), STAT=ierr)
        CALL LogMemAlloc('SpinInvBRR', NBASIS, 4, this_routine, SpinInvBRRTag, ierr)

        SpinInvBRR(:) = 0

        t = 0
        do I = 1, NBASIS
            t = t + 1
            SpinInvBRR(BRR(I)) = t
        end do

        return

    END SUBROUTINE CreateSpinInvBRR