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cif数据要达到怎样的水平才具备发表文章的水平？例如残留峰的高低。
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| 在解晶体的时候，我们会遇到有些结构能解出来，可是数据部怎么好！而且总是那些好晶体出现这种情况！到底一些杂志要求cif数据要达到什么样的水平才可能会接收呢？虫子们，在你的研究当中可否遇到过这样的情况，大家出来交流一下！ |
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Inorg@USF
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小木虫(金币+0.5):给个红包，谢谢回帖交流
paopaomeng(金币+1,VIP+0):谢谢交流 8-29 09:00
小木虫(金币+0.5):给个红包，谢谢回帖交流
paopaomeng(金币+1,VIP+0):谢谢交流 8-29 09:00
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主要还是以Check cif之后的A, B类 alert为主。A类是必须消灭的，当然有合理的解释也是可以的。B类原则上需要消灭，但是如果对于晶体学数据要求不高的杂志，可以接受。 至于残峰，要看骨架原子的大小和位置。如果是出现在重原子附近的Q峰，基本上可以忽略或按无序论。如果q峰游离于骨架之外，可以考虑为溶剂，或为可忽略的残峰，当然这点要参考你的骨架可能组成，收敛值，R1值，GOOF值，etc和deepest hole值。 大概就这些吧。 |
2楼2009-08-29 02:57:35
yinpanchao
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3楼2009-08-29 06:55:13
etongtong
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waiy2001(金币+2,VIP+0):谢谢交流，xi2004老师都夸你了 8-29 11:01
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这个问题很具体,就是ACTA E的投稿标准,即Check cif之后的A, B类 alert为主。A/B类是必须消灭.但是还不够,还得过编辑的手工检测. 好晶体的数据有一些手工的判据,我在这里澄清一下,与大家共同学习讨论: Completed crystal structures must pass the following tests. 1 The bonds in the model must be chemically reasonable. Similar bonds should have similar geometries and match literature values. 2 There should be no atoms with displacement parameters that are non-positive definite, npd. The displacement parameters should be checked for signs of systematic error. For example, ellipsoids of several heavy atoms aligned in one direction may indicate the need for a better absorption correction. Nonspherical or large ellipsoids suggest that the model may need to include disorder. 3 The structure should be refined to convergence, that is the maximum shift/error ratio should be < 0.05. All non-hydrogen atoms should be refined with anisotropic displacement parameters provided that there are at least 10 data per parameter. Lower data-to-parameter ratios indicate that either the data were not collected to a high enough scattering angle, or that Friedel-related (or equivalent) data were not collected for a structure in a noncentrosymmetric space group. 4 Noncentrosymmetric space groups should be refined with the correct absolute structure. The sample must contain atoms with sufficient differences in anomalous scattering to yield a meaningful absolute structure result. For example, the absolute structure cannot be determined under either of the following conditions, only one type of atom (besides hydrogen) and any type of radiation, or only first row atoms while using Mo Kα radiation. Also the data must be collected with sufficient quality (sufficient count times) to produce large (>10) mean F2/σ. The best test for absolute structure is the Flack test.6 5 The weighting scheme should be adjusted so as to produce nearly constant values for the variances as functions of intensity and resolution. Doing this will also make the goodness of fit, S, have a value around 1.0. 6 There should be no peaks with strong intensities in a list of "worst-fitting data." 7 The final difference map should have no abnormally high peaks or low valleys. 8 The final R1 and wR2 should be reasonably low for the quality of data. Good small molecule crystal structures usually have R1 < 0.05. Acceptable small molecule crystal structures typically have R1 < 0.10. -------------------------------------------------------------------------------- References 1 G. M. Sheldrick, SHELXTL Reference Manual, 1997, Bruker-AXS, Inc., Madison, WI 2 A. J. C. Wilson, Acta Cryst., 1976, A32, 994-996. 3 H. D. Flack & D. Schwarzenbach, 1988 Acta Cryst., 1988, A44 499-506. 4 W. C. Hamilton, Acta Cryst., 1965, 18, 502-510. 5 D. Rogers, Acta Cryst., 1981, A37, 734-741. 6 H. D. Flack, Acta Cryst., 1983, A39 876-881. 7 E. Parthe & L. M. Gelato, Acta Cryst., 1984, A40,169-183. 8 C. Bernardinelli & H. D. Flack, Acta Cryst., 1985, A41, 500-511 |
4楼2009-08-29 09:35:26
xi2004
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5楼2009-08-29 10:16:37
Inorg@USF
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6楼2009-08-29 13:12:08