PROC-NAME: GOODF01 Type_1/2

PURPOSE: To check that _refine_ls_goodness_of_fit_ref is within expected limits.

PROCEDURE:

TEST

(Type_2)

IF _refine_ls_goodness_of_fit_ref < 0.4 OR > 6.0 issue ALERT A

? ? ? ? ?"Alert A The least squares goodness of fit parameter lies outside the range 0.40 <> 6.00"

< 0.6 OR > 4.0 issue ALERT B

? ? ? ? ?"Alert B The least squares goodness of fit parameter lies outside the range 0.60 <> 4.00"

< 0.8 OR > 2.0 issue ALERT C

? ? ? ? ?"Alert C The least squares goodness of fit parameter lies outside the range 0.80 <> 2.00"

? ? ? ? Ideally, the goodness of fit (or standard deviation of an observation of unit weight) should be as close to 1.0 as possible. Values that deviate significantly from 1.0 may be an indication of one of the following: (a) the model is incorrect or incomplete or has been inadequately developed to account for disorder or solvent; (b) the reflection data are poor or weak; (c) there is twinning which has not been allowed for where overlap from the second twin domain (which may have been ignored in the data collection) causes errors in the intensities of some reflections; (d) the absorption corrections are inadequate; (e) the weighting scheme is inappropriate.

? ? ? ? Users of SHELXL should normally obtain goodness of fit values very close to 1.0 if none of the above features is relevant. If this is not the case, check that the weighting scheme co-efficients recommended by the program have been updated immediately prior to the last refinement run. If only the weights proposed when the model was in an early stage of development are used and not subsequently updated, the goodness of fit might deviate significantly from 1.0 and the weights should be updated.

? ? ? ? Users of other refinement software, particularly older programs or with refinement on F, might routinely obtain values for the goodness of fit in the range 1.5-2.5. This is acceptable, but authors need to be satisfied that this range for the goodness of fit is normal for good structures determined in their laboratory. However, values for the goodness of fit that are significantly smaller than 1.0 are usually a symptom of other problems with the data or model.

IF _refine_ls_goodness_of_fit_obs has been used issue a General ALERT

? ? ? ? ? ?"_refine_ls_goodness_of_fit_obs is an old dataname which has been superceded by _refine_ls_goodness_of_fit_ref" (Type_1)

? ? ? ? You are using an "old-fashioned", but still legal data name: _refine_ls_goodness_of_fit_obs. Please update the item to match the currently preferred name of _refine_ls_goodness_of_fit_ref. To ease this problem for the future, it is recommended that you upgrade or modify your CIF generating software accordingly.

(http://journals.iucr.org/services/cif/checking/GOODF_01.html)

目的：檢查_refine_ls_goodness_of_fit_ref是否在預(yù)期范圍內(nèi)。

過程：

檢查

(Type_2)

若_refine_ls_goodness_of_fit_ref小于0.4或大于6.0 則發(fā)布A類警告

? ? ? ?? "Alert A The least squares goodness of fit parameter lies outside the range 0.40 <> 6.00"

若_refine_ls_goodness_of_fit_ref小于0.6或大于4.0 則發(fā)布B類警告

? ? ? ?? "Alert B The least squares goodness of fit parameter lies outside the range 0.60 <> 4.00"

若_refine_ls_goodness_of_fit_ref小于0.8或大于2.0 則發(fā)布C類警告

? ? ? ?? "Alert C The least squares goodness of fit parameter lies outside the range 0.80 <> 2.00"

? ? ? ? 理想情況下，擬合優(yōu)度(或稱單位重量觀測值的標準偏差)應(yīng)盡可能接近1.0。若該值明顯偏離1.0，則可能表示存在下列情形之一：(a)模型不正確或不完整，或者由于考慮到無序或溶劑而建模不完整；(b)衍射數(shù)據(jù)差或若；(c) 由于第二孿晶組分(在數(shù)據(jù)收集中可能已被忽略)的重疊引起某些衍射點的強度出現(xiàn)錯誤而導(dǎo)致不被允許的孿晶；(d)吸收校正不充分；(e)權(quán)重方案不合適。

? ? ? ? 若無上述情形之一，則SHELXL用戶通常應(yīng)獲得非常接近1.0的擬合優(yōu)度數(shù)值。若非如此，請檢查程序建議的權(quán)重方案系數(shù)是否在上一次精修運行之前立即更新。若僅使用模型初期解析時建議的權(quán)重方案而不隨后進行更新，則擬合優(yōu)度可能會明顯偏離1.0，應(yīng)當更新權(quán)重方案。

? ? ? ? 使用其他精修軟件(尤其是舊版的程序或基于F精修的程序)的用戶可能通常會得到處于1.5-2.5范圍的擬合優(yōu)度值。這是可以接受的，但作者需要滿足的是，對于實驗室確定的良好結(jié)構(gòu)，擬合優(yōu)度的這個范圍是正常的。然而，顯著小于1.0的擬合優(yōu)度值通常是數(shù)據(jù)或模型存在其他問題的征兆。

若使用了_refine_ls_goodness_of_fit_obs則發(fā)布一般警告

? ? ? ?? "_refine_ls_goodness_of_fit_obs is an old dataname which has been superceded by _refine_ls_goodness_of_fit_ref" (Type_1)

? ? ? ? 請更新該條目，以匹配當前首選使用的名稱_refine_ls_goodness_of_fit_ref。為了將來緩解此問題，建議相應(yīng)地升級或更改CIF生成軟件。

警告原因：擬合優(yōu)度值(GooF值或S值)超出預(yù)期范圍。

解決策略：按上述藍色文字檢查數(shù)據(jù)或模型，根據(jù)具體問題進行改正，例如更新權(quán)重方案等。