An X-ray diffraction study of the structure of guanidinium aluminum sulfate hexahydrate

The Busing-Levy IBM 704 least squares program has been applied to three-dimensional X-ray diffraction data from crystals of guanidinium aluminum sulfate hexahydrate taken with the Bond-Benedict single-crystal automatic diffractometer. Indications of interactions between parameters were evident in the early stages of refinement and were not removed in the subsequent cycles. Strong interactions were subsequently corroborated by large values of many of the correlation coefficients of pairs of parameters. In this case these interactions prevent refinement. The correctness of the general features of the structure as given in a previous paper on the gallium isomorph is nevertheless corroborated by the present investigation. To enable those who have had similar difficulties to compare results, a fairly detailed account is given of the course of the attempt to refine the structure. The effects of highly correlated parameters are emphasized.