CheckCIF-CHEMW01

PROC-NAME: CHEMW01 Type_1

PURPOSE: To check that the _chemical_formula_weight matches that calculated for the _chemical_formula_sum.

PROCEDURE:

SUMMATION

(1) match the element symbols in _chemical_formula_sum

with values for _atom_type_symbol [NOT USED]

(2) multiply the number of atoms in _chemical_formula_sum

by the mass for this element

CALCULATE

RW = _chemical_formula_weight / SUM of (2)

DW = | _chemical_formula_weight - SUM of (2)|

TEST

IF RW

0.90 < > 1.10 issue ALERT A (> 10% difference)

         "Alert A The ratio of given/expected molecular weight as calculated from the _chemical_formula_sum lies outside the range 0.90 <> 1.10 "

0.95 < > 1.05 issue ALERT B (> 5% difference)

         "Alert B The ratio of given/expected molecular weight as calculated from the _chemical_formula_sum lies outside the range 0.95 <> 1.05 "

0.99 < > 1.01 issue ALERT C (> 1% difference)

         "Alert C The ratio of given/expected molecular weight as calculated from the _chemical_formula_sum lies outside the range 0.99 < > 1.01 "

IF DW > 1.0 and category is FO, FM, CO or CM

issue ALERT C

         "Alert C The difference between the given and expected weight for compound is greater 1 mass unit. Check that all hydrogen atoms have been taken into account."

        The formula weight given in the CIF differs from that calculated using the formula in _chemical_formula_sum. Check that (a) you have calculated the formula weight correctly and (b) that _chemical_formula_sum is correctly and fully specified. Remember that _chemical_formula_sum and _chemical_formula_weight must correspond with the true sum of all elements in all distinct moieties present, including any solvent and all H atoms, and not the contents implied by the model if there are differences due to the omission of a few H atoms or solvent atoms.

        If multiple moieties such as solvent are present, or one of the moieties possesses or is disordered about a crystallographic symmetry element, ensure that the correct ratio of moieties has been allowed for in the calculation of Z, _chemical_formula_sum and the formula weight.

        _chemical_formula_sum must also be in the correct format (e.g. do not use subscript formatting: C10 H20 is correct, C~10~ H~20~ is not).

(http://journals.iucr.org/services/cif/checking/CHEMW_01.html)

目的: 检查分子量(_chemical_formula_weight)与从化学分子式总和(_chemical_formula_sum)计算的结果是否一致。

若RW小于0.90或大于1.10(即大于10%的误差)，则发布A类警告

         "Alert A The ratio of given/expected molecular weight as calculated from the _chemical_formula_sum lies outside the range 0.90 <> 1.10 "

若RW小于0.95或大于1.05(即大于5%的误差)，则发布B类警告

         "Alert B The ratio of given/expected molecular weight as calculated from the _chemical_formula_sum lies outside the range 0.95 <> 1.05 "

若RW小于0.99或大于1.01(即大于1%的误差)，则发布C类警告

         "Alert C The ratio of given/expected molecular weight as calculated from the _chemical_formula_sum lies outside the range 0.99 < > 1.01 "

若DW大于1.0并且类别为FO、FM、CO或CM，则发布C类警告

         "Alert C The difference between the given and expected weight for compound is greater 1 mass unit. Check that all hydrogen atoms have been taken into account."

        CIF给出的分子量与从化学分子式总(_chemical_formula_sum)和计算得到的结果不一致。则检查(a)是否正确地计算了分子式，(b)是否正确并完整地给出了化学分子式总和(_chemical_formula_sum)。记住化学分子式总和(_chemical_formula_sum)与化学分子量(_chemical_formula_weight)必须和存在的不同部分中所有元素的真实总和一致，包括任何溶剂和所有氢原子。如果是由于删除了少许氢原子或溶剂原子而导致的差异，则不对应于模型所暗示的内容。

        若存在多个组分例如溶剂，或者其中一个组分具有无序或关于晶体学对称元素无序，则要确保在计算Z值和化学式总(_chemical_formula_sum)时各组分的比例为正确且允许的。

        化学式总和(_chemical_formula_sum)必须使用正确的格式(例如不要使用下标格式：C10 H20是正确的格式；而C~10~ H~20~是错误的格式)。

例：CHEMW01_ALERT_1_A The ratio of given/expected molecular weight as calculated from the _chemical_formula_sum lies outside the range 0.90 <> 1.10

Calculated formula weight = 585.3216

Formula weight given = 1324.8300

警告原因：分子式不对。

解决策略：在ins里给对分子式和Z值重新精修生成CIF。若使用Olex2软件，则可填好Z'后精修重新生成CIF即可。