Electron diffraction study of the validity of the Th6 space group for solid carbon dioxide
Electron diffraction patterns obtained with 65 kV electrons (wavelength = 0.0466 Å) from polycrystalline carbon dioxide at about 77 °K are in reasonable agreement with the patterns to be expected from a lattice having the accepted Th6 symmetry of solid carbon dioxide. The calculated and observed intensities of the rings agree, provided the parameter u which measures the separation of adjacent carbon and oxygen atoms is taken to be larger than u = 0.1083 which was obtained from earlier X-ray work. Agreement between experiment and theory is obtained for u such that 0.1083 < u < 0.1250 but further work is required if u is to be determined precisely.Detailed consideration is given to those rings for which H = √17 and H = √18, where H = √(h2 + k2 + l2). In the present experiments the observed intensities of these rings agree with the calculated intensities but similar agreement was not found in earlier X-ray diffraction work.