Nuclear displacement operators calculations

As Figure 2 shows, the two models differ only by a vertical displacement, which is a measure of the difference in the mean square interparticle dipolar fields (second moments) operative in the two models. The values of these mean square local fields can be calculated easily from the minimum value of Ti or from the rigid lattice values of T2. Because of the 1000-fold ratio between electronic and nuclear magnetic moments, even... 

It is possible that this peculiarity of rod insertion was the final mechanism for the prompt critical accident. The calculation of the size of the effect depends upon assumptions about the previous operating history of the reactor, but estimates made at the Berkeley Nuclear Laboratory suggest that this final water displacement may have added between Vi% and Vi% reactivity, enough indeed to bring about the prompt critical excursion. 

A number of approximate VCD models are based on electronic structure calculations. The LMO modeH is a more accurate molecular orbital (MO) approach in evaluation of VCD intensities and has been implemented at the ab initio level. The nuclear and the electronic contributions to the dipole transition moments are treated completely separately in this model. The expressions of nuclear contributions are derived with full nuclear charges. For the expression of the electronic contributions, the BO approximation is invoked after the electronic part of the magnetic dipole operator is modified in such a way that the BO difficulty is avoided. Nonvanishing electronic contributions to the magnetic transition moments are thus obtained, which come from the displacements of the centroids of the localized MOs during vibrations. 

---