<xsd:complexType name="chemical_formulaType">
<xsd:annotation>
<xsd:documentation xml:lang="en">Data items in the CHEMICAL_FORMULA category would not, in general, be used in a macromolecular CIF. See instead the ENTITY data items. Data items in the CHEMICAL_FORMULA category specify the composition and chemical properties of the compound. The formula data items must agree with those that specify the density, unit-cell and Z values. The following rules apply to the construction of the data items _chemical_formula.analytical, _chemical_formula.structural and attribute sum in category chemical_formula. For the data item attribute moiety in category chemical_formula, the formula construction is broken up into residues or moieties, i.e. groups of atoms that form a molecular unit or molecular ion. The rules given below apply within each moiety but different requirements apply to the way that moieties are connected (see attribute moiety). in category chemical_formula (1) Only recognized element symbols may be used. (2) Each element symbol is followed by a 'count' number. A count of '1' may be omitted. (3) A space or parenthesis must separate each cluster of (element symbol + count). (4) Where a group of elements is enclosed in parentheses, the multiplier for the group must follow the closing parenthesis. That is, all element and group multipliers are assumed to be printed as subscripted numbers. (An exception to this rule exists for attribute moiety in category chemical_formula formulae where pre- and post-multipliers are permitted for molecular units.) (5) Unless the elements are ordered in a manner that corresponds to their chemical structure, as in attribute structural in category chemical_formula, the order of the elements within any group or moiety should be: C, then H, then the other elements in alphabetical order of their symbol. This is the 'Hill' system used by Chemical Abstracts. This ordering is used in _chemical_formula.moiety and _chemical_formula.sum. Example 2 - based on data set TOZ of Willis, Beckwith & Tozer [(1991). Acta Cryst. C47, 2276-2277]. <PDBx:chemical_formulaCategory> <PDBx:chemical_formula entry_id="TOZ"> <PDBx:moiety>C18 H25 N O3</PDBx:moiety> <PDBx:sum>C18 H25 N O3</PDBx:sum> <PDBx:weight>303.40</PDBx:weight> </PDBx:chemical_formula> </PDBx:chemical_formulaCategory></xsd:documentation>
</xsd:annotation>
<xsd:sequence>
<xsd:element name="chemical_formula" minOccurs="0" maxOccurs="unbounded">
<xsd:complexType>
<xsd:all>
<xsd:element name="analytical" minOccurs="0" maxOccurs="1" nillable="true" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">Formula determined by standard chemical analysis including trace elements. See the CHEMICAL_FORMULA category description for rules for writing chemical formulae. Parentheses are used only for standard uncertainties (estimated standard deviations). Fe2.45(2) Ni1.60(3) S4</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="iupac" minOccurs="0" maxOccurs="1" nillable="true" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">Formula expressed in conformance with IUPAC rules for inorganic and metal-organic compounds where these conflict with the rules for any other CHEMICAL_FORMULA entries. Typically used for formatting a formula in accordance with journal rules. This should appear in the data block in addition to the most appropriate of the other CHEMICAL_FORMULA data names. Ref: IUPAC (1990). Nomenclature of Inorganic Chemistry. Oxford: Blackwell Scientific Publications. [Co Re (C12 H22 P)2 (C O)6].0.5C H3 O H</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="moiety" minOccurs="0" maxOccurs="1" nillable="true" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">Formula with each discrete bonded residue or ion shown as a separate moiety. See the CHEMICAL_FORMULA category description for rules for writing chemical formulae. In addition to the general formulae requirements, the following rules apply: (1) Moieties are separated by commas ','. (2) The order of elements within a moiety follows general rule (5) in the CHEMICAL_FORMULA category description. (3) Parentheses are not used within moieties but may surround a moiety. Parentheses may not be nested. (4) Charges should be placed at the end of the moiety. The charge '+' or '-' may be preceded by a numerical multiplier and should be separated from the last (element symbol + count) by a space. Pre- or post-multipliers may be used for individual moieties. C7 H4 Cl Hg N O3 S C12 H17 N4 O S 1+, C6 H2 N3 O7 1- C12 H16 N2 O6, 5(H2 O1) (Cd 2+)3, (C6 N6 Cr 3-)2, 2(H2 O)</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="structural" minOccurs="0" maxOccurs="1" nillable="true" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">See the CHEMICAL_FORMULA category description for the rules for writing chemical formulae for inorganics, organometallics, metal complexes etc., in which bonded groups are preserved as discrete entities within parentheses, with post-multipliers as required. The order of the elements should give as much information as possible about the chemical structure. Parentheses may be used and nested as required. This formula should correspond to the structure as actually reported, i.e. trace elements not included in atom-type and atom-site data should not be included in this formula (see also attribute analytical) in category chemical_formula. Ca ((Cl O3)2 O)2 (H2 O)6 (Pt (N H3)2 (C5 H7 N3 O)2) (Cl O4)2</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="sum" minOccurs="0" maxOccurs="1" nillable="true" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">See the CHEMICAL_FORMULA category description for the rules for writing chemical formulae in which all discrete bonded residues and ions are summed over the constituent elements, following the ordering given in general rule (5) in the CHEMICAL_FORMULA category description. Parentheses are not normally used. C18 H19 N7 O8 S</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="weight" minOccurs="0" maxOccurs="1" nillable="true">
<xsd:annotation>
<xsd:documentation xml:lang="en">Formula mass in daltons. This mass should correspond to the formulae given under attribute structural, in category chemical_formula _chemical_formula.moiety or _chemical_formula.sum and, together with the Z value and cell parameters, should yield the density given as attribute density_diffrn in category exptl_crystal.</xsd:documentation>
</xsd:annotation>
<xsd:simpleType>
<xsd:restriction base="xsd:decimal">
<xsd:minInclusive value="1.0"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
<xsd:element name="weight_meas" minOccurs="0" maxOccurs="1" nillable="true">
<xsd:annotation>
<xsd:documentation xml:lang="en">Formula mass in daltons measured by a non-diffraction experiment.</xsd:documentation>
</xsd:annotation>
<xsd:simpleType>
<xsd:restriction base="xsd:decimal">
<xsd:minInclusive value="1.0"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
</xsd:all>
<xsd:attribute name="entry_id" use="required" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">This data item is a pointer to attribute id in category entry in the ENTRY category.</xsd:documentation>
</xsd:annotation>
</xsd:attribute>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType> |