Cal ions

Iditional importance is that the vibrational modes are dependent upon the reciprocal e vector k. As with calculations of the electronic structure of periodic lattices these cal-ions are usually performed by selecting a suitable set of points from within the Brillouin. For periodic solids it is necessary to take this periodicity into account the effect on the id-derivative matrix is that each element x] needs to be multiplied by the phase factor k-r y). A phonon dispersion curve indicates how the phonon frequencies vary over tlie luin zone, an example being shown in Figure 5.37. The phonon density of states is ariation in the number of frequencies as a function of frequency. A purely transverse ition is one where the displacement of the atoms is perpendicular to the direction of on of the wave in a pmely longitudinal vibration tlie atomic displacements are in the ition of the wave motion. Such motions can be observed in simple systems (e.g. those contain just one or two atoms per unit cell) but for general three-dimensional lattices of the vibrations are a mixture of transverse and longitudinal motions, the exceptions... 

The two, independent, Cal+ ions are octahe-drally coordinated. Two of the coordination sites around each Ca2+ ion involve oxygen atoms of phosphate groups from two different GpC dimers, and the remaining sites are occupied by water molecules. The conformational structures of CaGpC and NaGpC10 are very similar. 

Fig. 11, Effect of increasing electron demand on the rates of solvolysis of 7-arylnor-bornyl (.303) and 7-aryl-anfi-norbornenyl p-nitrobenzoates (304). [Reproduced from Brown, H. G The nonclassi-cal ion problem. New York Plenum Press 1977.1...

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