CML element symmetry

Abstract	false (This can be used in an instance)
Nillable	false (Instance values cannot use xsi:nil)
Target Namespace	http://www.xml-cml.org/schema/cml2/core
Declared Namespaces	xmlns:val=http://www.w3.org/1999/XSL/TransformX xmlns:stm=http://www.xml-cml.org/schema/stmml xmlns:xsd=http://www.w3.org/2001/XMLSchema xmlns:xlink=http://www.w3.org/1999/xlink xmlns:cml=http://www.xml-cml.org/schema/cml2/core xmlns=http://www.xml-cml.org/schema/cml2/core

<xsd:element name="symmetry" id="el.symmetry">
    <xsd:annotation>
        <xsd:documentation>
            <div class="summary">Molecular, crystallographic or other symmetry.</div>
            <div class="description">
                <p>
                    <tt>symmetry</tt>
provides a label and/or symmetry operations for molecules
or crystals. Point and spacegroups can be specified by strings, though these are not
enumerated, because of variability in syntax (spaces, case-sensitivity, etc.),
potential high symmetries (e.g. TMV disk is D17) and
non-standard spacegroup settings. Provision is made for explicit symmetry operations
through <matrix> child elements.
                </p>
                <p>
By default the axes of symmetry are defined by the symbol - thus C2v requires
z to be the unique axis, while P21/c requires b/y. Spacegroups imply the semantics
defined in International Tables for Crystallography, (Int Union for Cryst., Munksgaard).
Point groups are also defined therein.
                </p>
                <p>
The element may also be used to give a label for the symmetry species (irreducible
representation) such as "A1u" for a vibration or orbital.
                </p>
                <p>
The matrices should be 3x3 for point group operators and 3x4 for spacegroup operators.
The use of crystallographic notation ("x,1/2+y,-z") is not supported - this would
be <matrix>1 0 0 0.0 0 1 0 0.5 0 0 1 0.0<matrix>.
                </p>
                <p>The default convention for point group symmetry is
                    <tt>Schoenflies</tt>
and for
spacegroups is "H-M". Other conventions (e.g. "Hall") must be specfied through
the
                    <tt>convention</tt>
attribute.
</p>
                <p>
This element implies that the Cartesians or fractional coordinates in a molecule
are oriented appropriately. In some cases it may be useful to specify the symmetry of
an arbitarily oriented molecule and the <molecule> element has the attribute
                    <tt>symmetryOriented</tt>
for this purpose.
</p>
            </div>
            <div class="example">
                <pre>
<cml title="symmetry example 1">
<symmetry pointGroup="C2v" id="s1">
<matrix id="e" rows="3" columns="3" dataType="xsd:float" matrixType="rotation33">
1 0 0
0 1 0
0 0 1
</matrix>
<matrix id="c2" rows="3" columns="3" dataType="xsd:float" matrixType="rotation33">
-1 0 0
0 -1 0
0 0 1
</matrix>
<matrix id="sx" rows="3" columns="3" dataType="xsd:float" matrixType="rotation33">
-1 0 0
0 1 0
0 0 1
</matrix>
<matrix id="sy" rows="3" columns="3" dataType="xsd:float" matrixType="rotation33">
1 0 0
0 -1 0
0 0 1
</matrix>
</symmetry>
</cml>
                </pre>
            </div>
        </xsd:documentation>
    </xsd:annotation>
    <xsd:complexType>
        <xsd:sequence>
            <xsd:element ref="matrix" minOccurs="0" maxOccurs="unbounded"/>
        </xsd:sequence>
        <xsd:attributeGroup ref="dictRef"/>
        <xsd:attributeGroup ref="convention"/>
        <xsd:attributeGroup ref="title"/>
        <xsd:attributeGroup ref="id"/>
        <xsd:attribute name="pointGroup" type="xsd:string">
            <xsd:annotation>
                <xsd:documentation>
                    <div class="summary">A point group.</div>
                    <div class="description">No fixed semantics, though Schoenflies is recommended over Hermann-Mauguin. We may provide a controlled-extensible list in the future.</div>
                </xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
        <xsd:attribute name="spaceGroup" type="xsd:string">
            <xsd:annotation>
                <xsd:documentation>
                    <div class="summary">A point group.</div>
                    <div class="description">No fixed semantics, though Hermann-Mauguin or Hall is recommended over Schoenflies. We may provide a controlled-extensible list in the future.</div>
                </xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
        <xsd:attribute name="irreducibleRepresentation" type="xsd:string">
            <xsd:annotation>
                <xsd:documentation>
                    <div class="summary">A symmetry species.</div>
                    <div class="description">No fixed semantics, though we may provide a controlled-extensible list in the future.</div>
                </xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
        <xsd:attribute name="number" type="xsd:nonNegativeInteger">
            <xsd:annotation>
                <xsd:documentation>
                    <div class="curation">2003-03-30: added number attribute</div>
                    <div class="summary">The rotational symmetry number</div>
                    <div class="description">Used for calculation of entropy, etc.</div>
                </xsd:documentation>
            </xsd:annotation>
        </xsd:attribute>
    </xsd:complexType>
</xsd:element>

symmetry provides a label and/or symmetry operations for molecules or crystals. Point and spacegroups can be specified by strings, though these are not enumerated, because of variability in syntax (spaces, case-sensitivity, etc.), potential high symmetries (e.g. TMV disk is D17) and non-standard spacegroup settings. Provision is made for explicit symmetry operations through child elements.

By default the axes of symmetry are defined by the symbol - thus C2v requires z to be the unique axis, while P21/c requires b/y. Spacegroups imply the semantics defined in International Tables for Crystallography, (Int Union for Cryst., Munksgaard). Point groups are also defined therein.

The element may also be used to give a label for the symmetry species (irreducible representation) such as "A1u" for a vibration or orbital.

The matrices should be 3x3 for point group operators and 3x4 for spacegroup operators. The use of crystallographic notation ("x,1/2+y,-z") is not supported - this would be 1 0 0 0.0 0 1 0 0.5 0 0 1 0.0.

The default convention for point group symmetry is Schoenflies and for spacegroups is "H-M". Other conventions (e.g. "Hall") must be specfied through the convention attribute.

This element implies that the Cartesians or fractional coordinates in a molecule are oriented appropriately. In some cases it may be useful to specify the symmetry of an arbitarily oriented molecule and the element has the attribute symmetryOriented for this purpose.

element {http://www.xml-cml.org/schema/cml2/core}symmetry

Source

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