In work by Xie and co-workers , where the coupling was calculated using the generalised Mulliken-Hush model the clusters display sufficiently small electron-hole overlap and large excitonic radii, allowing the generalised Mulliken-Hush model to be applicable. Using a four-point model for their reorganisation energy, rate constants of 2.55×10 10 s -1 , 1.48×10 8 s -1 , 1.61×10 13 s -1 , and 2.00×10 12 s -1 , were found for cadmium selanide clusters 3-D 3h , 4-D 4h , 4-T d , and 3-C 3v , respectively (Figure ). Later work by Xie and co-workers found for larger cadmium selanide quantum dots rates of 4.80×10 11 s -1 , 2.65×10 14 s -1 , 3.63×10 14 s -1 , and 3.66×10 7 s -1 , for compounds A, B, C, and D, respectively. For these compounds, it was determined that the size and conformation of each quantum dot that was the determining factor with respect to the speed of internal conversion. However, in the latter study, the internal conversion is correlated with the local softness ; either exalted by cadmium's electrophilicity, or damped by the selanide's nucleophilicity. Swenson and co-workers note the importance of binding geometries with respect to the ligand. With respect to CdSe nanoclusters, less rigid structures result in larger changes in Huang-Rhys factors, increasing the rate of internal conversion, in some cases by several orders of magnitude (Figure ). Du and co-workers use the formalism to study ZnSe dots; no pattern was clearly noted. Internal conversion was seen to oscillate wildly as cluster size increased. Clusters of size 4, 6, and 13 were reported to have rates on the order of 10 13 s -1 , while those of size 3, 5, and 11 all had rates on the order of 10 8 s -1 . Further in-depth analysis did however find a strong relationship between the cluster size and rate of internal conversion based on the reorganisation energy.