get_optimal_correlation_factor Function

    function get_optimal_correlation_factor() result(corr_factor)
        ! Hongjuns derivation was for the k-space hubbard and in the low
        ! density and U limit though..
        real(dp) :: corr_factor
#ifdef DEBUG_
        character(*), parameter :: this_routine = "get_optimal_correlation_factor"
#endif

        ASSERT(associated(lat))

        ! the sign is not quite sure here.. which i need to take to
        ! calculate the hermitian matrix elements..
        corr_factor = -log(abs(real(uhub, dp) / real(4 * lat%get_ndim() * bhub, dp)) + 1.0_dp)

    end function get_optimal_correlation_factor