However, while both MVG and LG calculations of the total OR are (or can be made) origin invariant, this does not necessarily ensure that individual Sia values will be origin invariant. The total OR is in general made origin invariant via cancellation, rather than elimination, of the origin dependent terms from each Sia value. It is possible that choosing a physically meaningful origin like the center of mass may produce reasonable Sia values, though this is not guaranteed; e.g. typical LG CCSD calculations of the total OR are origin dependent and using the center of mass as the origin does not consistently lead to high accuracy in comparison with experiment . In any case, the reliability of the physical interpretations provided by the Sia analysis would be greatly improved by removing this origin dependence altogether.