Fig. 4 presents details of the coordination of selected atoms; an alternative view is presented in the form of RDF's, averaged over the whole trajectory and over all atoms in a particular position (Fig. 5 and 6). The RDF's for yttrium feature a sharp and narrow peak indicating the well-defined Y¨CF distance in the first coordination sphere. In contrast, RDF's for sodium show broader and shorter peaks, which indicate more variability of distances. The RDF's of P6" C:Na and P6"2m B:Na share a characteristic broadening of the first peak, which may result from oscillations towards the adjacent six-fold coordination sites. In general, RDF's of P6" and P6"2m look very similar. The first peak of the C:Na RDF in the P63/m model has no broadening at the base, since the atoms occupy the six-fold coordination sites.
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