Isomer diffraction pattern, calculated

The molecular scattering patterns, sM(s), for cluster sizes n = 37 to 39,43 and 55 were fitted to structures calculated [17] by I.L. Garzon and K. Michaelian, Instituto de Ffsica, Universidad Nacional Autdnoma de Mexico. Structures for 6 to 10 lowest energy isomers were calculated for each cluster size by density functional theory. The best fit of the diffraction pattern data to patterns calculated for the isomers of each cluster size was found to occur for only a single isomer structure although the... 

In many respects, these experiments are allowing us to explore new and exciting science. The most intriguing and unexpected result of the metal cluster studies is that most of the available structural isomers do not appear to contribute to the measured diffraction patterns. Perhaps even more remarkable is that the comparison of diffraction data with calculated structures is capable of identifying a single best... 

In addition, an interesting, although negative, result has come from powder diffraction studies of the hexachloro compounds. We have examined Debye—Scherrer photographs of several samples known to contain predominantly hexachlorodibenzo-p-dioxins and have identified the patterns of at least three crystalline phases therein. (There are 10 possible isomers of hexachlorodibenzo-p-dioxin.) These patterns have been checked carefully against the calculated d-spacings and intensities of the 1,2,3,7,8,9-hexa isomer described by Cantrell, Webb, and Mabis (I) and also against an observed pattern supplied by Cantrell and believed to be from the low temperature phase of the same material. Yet to date we... 

Diffraction data shown in Figure 7.11 for the size range n = 15-17 identify cage structures as best fits to calculated isomers at each size. Evidence for the cage structures at n = 16 and 17 has been observed recently in photoelectron measurements [31]. The cage structure associated with the best fit for n = 15 is not consistent with structures suggested by these photoelectron measurements. However, in this case, the best fit to a unique calculated pattern lends support to the diffraction result. 

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