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求助,单晶衍射数据吸收校正

作者 lihuiduan
来源: 小木虫 250 5 举报帖子
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Comments:The crystallography appears to be OK although for 2 there is a 3.5 e/A3 hole in the final difference map. This needs to be explained (where is it?). I also note that Table 1 indicates that no absorption correction was applied. This is not good practice unless the linear absorption coefficient is less than 1 so it is particularly a problem for 2 where the absorption coefficient is >7 (!!!). If no absorption correction was, in fact, used, that could explain the big hole noted above and if true, the refinement has to be redone with the absorption correction applied to the data.

Author’s answer: In compound 2, the largest diffraction hole of –3.499 e.Å–3 located at the coordinates [0.9554, 0.4582, 0.0000] was at a distance of 0.66 Å from I(3), which could be attributed to the thermal vibration and disordered structure of I(3).

Comments:The "explanation" for the large hole in the final difference map which I called attention to is really a "throwaway" comment. If it really is a "disorder in the I atom" as the authors suggest, then there have to be one or more additional sites in which the disordered I is found. I see no evidence that this possibility was dealt with. Given that the hole is < 1A from the I position, I suspect it is due to uncorrected anisotropic displacement of the I or to deficiencies in the absorption correction used. While the best solution would be to do a -indexed, analytical absorption correction, I suspect the authors did not collect the data necessary to do this and so would be willing to accept their present results PROVIDED that they inspect the difference map in the vicinity of the I atom and comment on its appearance in terms of residual peaks and holes (i.e. along the lines of Figs. 16.3-16.5 of Stout & Jensen, "X-ray Structure Determination&quot. 返回小木虫查看更多

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  • lich666

    这个最好找你给你测试的老师,有工作站的软件可以弄。

  • 我想更懂你29

    测试的软件上一般会有吸收矫正的软件,你找测试的工程师,跟他说明情况,要他给你做

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