CheckCIF-DENSD01

PROC-NAME: DENSD01 Type_1

PURPOSE: To check that the _exptl_crystal_density_diffrn matches the _cell_volume and _chemical_formula_weight values

PROCEDURE:

CALCULATE

DEN = 1.66042 * _chemical_formula_weight * _cell_formula_units_Z / _cell_volume

RD = _exptl_crystal_density_diffrn / DEN

TEST

IF RD 0.9 < > 1.1 issue ALERT A

         "Alert A The ratio of the submitted crystal density and that calculated from the formula is outside the range 0.90 < > 1.10 "

RD 0.95 < > 1.05 issue ALERT B

         "Alert B The ratio of the submitted crystal density and that calculated from the formula is outside the range 0.95 < > 1.05 "

RD 0.99 < > 1.01 issue ALERT C

         "Alert C The ratio of the submitted crystal density and that calculated from the formula is outside the range 0.99 < > 1.01 "

        The calculated density given in the CIF differs from that calculated using the specified formula weight and the stated number of formula units in the unit cell (Z). Check that (a) you have calculated the density correctly and (b) that _chemical_formula_weight and _cell_formula_units_Z are correctly specified. Remember that _chemical_formula_weight and the calculated density 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 and _chemical_formula_weight.

(http://journals.iucr.org/services/cif/checking/DENSD_01.html)

目的：检查_exptl_crystal_density_diffrn是否与_cell_volume _chemical_formula_weight的值相匹配。

过程：

计算

DEN = 1.66042 * _chemical_formula_weight * _cell_formula_units_Z / _cell_volume

RD = _exptl_crystal_density_diffrn / DEN

检查

若RD小于0.9或大于1.1则发布A级警告

         "Alert A The ratio of the submitted crystal density and that calculated from the formula is outside the range 0.90 < > 1.10 "

若RD小于0.95或大于1.05则发布B级警告

         "Alert B The ratio of the submitted crystal density and that calculated from the formula is outside the range 0.95 < > 1.05 "

若RD小于0.99或大于1.01则发布C级警告

         "Alert C The ratio of the submitted crystal density and that calculated from the formula is outside the range 0.99 < > 1.01 "

        CIF中给出的密度计算值与使用指定分子量和单胞中所含分子单元的数目(Z)所计算的密度值不同。请检查：(a)你已正确计算该密度值；(b) _chemical_formula_weight和_cell_formula_units_Z指定正确。请记住，_chemical_formula_weight和该密度计算值必须与所有不同部分中所有元素的真实总和相对应，包括任何溶剂和所有氢原子，若由于删除了一些氢原子或溶剂原子而存在差异，则不应与模型所暗示的内容相对应。

        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、化学式总和(_chemical_formula_sum)以及线性吸收系数值时各组分的比例为正确且允许的。

例：DENSD01_ALERT_1_A The ratio of the submitted crystal density and that calculated from the formula is outside the range 0.90 <> 1.10

Crystal density given    = 1.719

Calculated crystal density = 1.422

警告原因：分子式和Z值未填写正确。

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。