<xsd:complexType name="pdbx_reflns_twinType">
<xsd:annotation>
<xsd:documentation xml:lang="en">Details decribing crystallographic twinning. Example 1 - <PDBx:pdbx_reflns_twinCategory> <PDBx:pdbx_reflns_twin crystal_id="1" diffrn_id="1" operator="h,-h-k,-l"> <PDBx:fraction>.43</PDBx:fraction> <PDBx:mean_F_square_over_mean_F2>.84</PDBx:mean_F_square_over_mean_F2> <PDBx:mean_I2_over_mean_I_square>1.3</PDBx:mean_I2_over_mean_I_square> <PDBx:type>merohedral</PDBx:type> </PDBx:pdbx_reflns_twin> </PDBx:pdbx_reflns_twinCategory></xsd:documentation>
</xsd:annotation>
<xsd:sequence>
<xsd:element name="pdbx_reflns_twin" minOccurs="0" maxOccurs="unbounded">
<xsd:complexType>
<xsd:all>
<xsd:element name="domain_id" minOccurs="0" maxOccurs="1" nillable="true" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">An identifier for the twin domain.</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="fraction" minOccurs="1" maxOccurs="1" nillable="true" type="xsd:decimal">
<xsd:annotation>
<xsd:documentation xml:lang="en">The twin fraction or twin factor represents a quantitative parameter for the crystal twinning. The value 0 represents no twinning, < 0.5 partial twinning, = 0.5 for perfect twinning.</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="mean_F_square_over_mean_F2" minOccurs="0" maxOccurs="1" nillable="true" type="xsd:decimal">
<xsd:annotation>
<xsd:documentation xml:lang="en">The ideal statistics for twinned crystals. The values calculated with the acentric data are given below. Statistic Untwinned data Perfect twinned data <I^2>/<I>^2 2.0 1.5 <F>^2/<F^2> 0.785 0.865 References: Yeates, T.O. (1997) Methods in Enzymology 276, 344-358. Detecting and Overcoming Crystal Twinning. and information from the following on-line sites: CNS site http://cns.csb.yale.edu/v1.1/ CCP4 site http://www.ccp4.ac.uk/dist/html/detwin.html SHELX site http://shelx.uni-ac.gwdg.de/~rherbst/twin.html</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="mean_I2_over_mean_I_square" minOccurs="0" maxOccurs="1" nillable="true" type="xsd:decimal">
<xsd:annotation>
<xsd:documentation xml:lang="en">The ideal statistics for twinned crystals. The values calculated with the acentric data are given below. Statistic Untwinned data Perfect twinned data <I^2>/<I>^2 2.0 1.5 <F>^2/<F^2> 0.785 0.865 References: Yeates, T.O. (1997) Methods in Enzymology 276, 344-358. Detecting and Overcoming Crystal Twinning. and information from the following on-line sites: CNS site http://cns.csb.yale.edu/v1.1/ CCP4 site http://www.ccp4.ac.uk/dist/html/detwin.html SHELX site http://shelx.uni-ac.gwdg.de/~rherbst/twin.html</xsd:documentation>
</xsd:annotation>
</xsd:element>
<xsd:element name="type" minOccurs="0" maxOccurs="1" nillable="true">
<xsd:annotation>
<xsd:documentation xml:lang="en">There are two types of twinning: merohedral or hemihedral non-merohedral or epitaxial For merohedral twinning the diffraction patterns from the different domains are completely superimposable. Hemihedral twinning is a special case of merohedral twinning. It only involves two distinct domains. Pseudo-merohedral twinning is a subclass merohedral twinning in which lattice is coincidentally superimposable. In the case of non-merohedral or epitaxial twinning the reciprocal lattices do not superimpose exactly. In this case the diffraction pattern consists of two (or more) interpenetrating lattices, which can in principle be separated.</xsd:documentation>
</xsd:annotation>
<xsd:simpleType>
<xsd:restriction base="xsd:string">
<xsd:enumeration value="merohedral"/>
<xsd:enumeration value="hemihedral"/>
<xsd:enumeration value="non-merohedral"/>
<xsd:enumeration value="pseudo-merohedral"/>
<xsd:enumeration value="epitaxial"/>
<xsd:enumeration value="tetartohedral"/>
</xsd:restriction>
</xsd:simpleType>
</xsd:element>
</xsd:all>
<xsd:attribute name="crystal_id" use="required" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">The crystal identifier. A reference to attribute id in category exptl_crystal in category EXPTL_CRYSTAL.</xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="diffrn_id" use="required" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">The diffraction data set identifier. A reference to attribute id in category diffrn in category DIFFRN.</xsd:documentation>
</xsd:annotation>
</xsd:attribute>
<xsd:attribute name="operator" use="required" type="xsd:string">
<xsd:annotation>
<xsd:documentation xml:lang="en">The possible merohedral or hemihedral twinning operators for different point groups are: True point group Twin operation hkl related to 3 2 along a,b h,-h-k,-l 2 along a*,b* h+k,-k,-l 2 along c -h,-k,l 4 2 along a,b,a*,b* h,-k,-l 6 2 along a,b,a*,b* h,-h-k,-l 321 2 along a*,b*,c -h,-k,l 312 2 along a,b,c -h,-k,l 23 4 along a,b,c k,-h,l References: Yeates, T.O. (1997) Methods in Enzymology 276, 344-358. Detecting and Overcoming Crystal Twinning. and information from the following on-line sites: CNS site http://cns.csb.yale.edu/v1.1/ CCP4 site http://www.ccp4.ac.uk/dist/html/detwin.html SHELX site http://shelx.uni-ac.gwdg.de/~rherbst/twin.html h,-h-k,-l h+k,-k,-l -h,-k,l h,-k,-l k,-h,l</xsd:documentation>
</xsd:annotation>
</xsd:attribute>
</xsd:complexType>
</xsd:element>
</xsd:sequence>
</xsd:complexType> |