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High resolution 60 and 100 Mc. NMR spectra have been obtained for a series of deuterated polypropenes with compounds of the highest sterical purity used. The fundamental parameters of the spectra (chemical shifts and coupling constants) have been accurately determined and compared with previous results available in the literature. The results may be applied to quantitative estimates of the stereoregularity of polymers not deuterated by the NMR method.

An analysis of three-and four-atom interactions of exchange type in first and second orders of perturbation theory is presented, on the basis of an effective-electron model with a Gaussian distribution of charge. The results are then applied to a determination of the three-and four-atom components of the crystal energy for close-packed rare-gas solids. It is found that both the three-and four-atom interactions favor a fee crystal structure. The magnitude of the four-atom energy relative to the three-atom component for a given atomic species and a given crystalline configuration is essentially a function only of the ratio between the second-and first-order pair interactions for nearest neighbors in the solid. For the most probable range of values of this ratio, the four-atom crystal energy is relatively unimportant. The sum of three-and four-atom crystal energies is found to vary little with the ratio. Calculated values for the stacking-fault energy in solid argon and xenon agree reasonably well with those obtained from observations on thin films of these solids.