On the Determination of the NiCl₂ Crystal Structure

Abstract

] has calculated the zero-field splitting parameter D of NiCl, and determined the crystal structure of NiC1, by using Zhao et al.'s model and fitting procedure [2]. Huang has demonstrated that Zhao et al.'s model cannot only interpret the zero-field splitting but also calculated the bond angle which is more exact than that determined by X-ray diffraction. However, Zheng [3] has critically pointed out that Zhao et al.'s model and fitting procedure are erroneous, and the results derived from the model and fitting procedure are unreliable. From the viewpoint of crystal structure, in this note we point out that the crystal structure of NiCl, determined by Huang is contrary to basic knowledge of crystal structure, so it is faulty. What we obtain is opposite to Huang's conclusion.By means In other words, the bond length and the bond angle determined by Huang are contrary to the geometric relation of the cystal structure, so the crystal structure of NiCI, determined by Huang is false.As is well-known, the EPR splitting parameter D is very sensitive to the bond angle 8, therefore a minute change of 8 will result in a bigger change of D [7]. Making use of the data of R and 8 determined by X-ray diffraction, the result D = -0.9 cm-' can be obtained with Huang's method. Comparing this value with the experimental D (= 1.35 cm-'), we can see the obvious difference. The signs of the two values are opposite and the relative error is 166%. Such a big error shows clearly that Zhao et al.'s fitting procedure is uneffective.With the same fitting method, Zhao and co-workers [8] have determined the crystal structure of MnF,. But the structural data determined by therm are contrary to the simple geometric relation of the crystal structure, so the crystal structure of MnF, determined by therm is false, as pointed out by Baur and Sharma [9].') Chengdu 610066, People's Republic of China.