2.3.3.1.37. NXchemical_composition

Status:

base class, extends NXobject

Description:

Chemical composition of a sample or a set of things.

Symbols:

The symbols used in the schema to specify e.g. dimensions of arrays.

n: The number of samples or things.

Groups cited:

NXatom

Structure:

normalization: (optional) NX_CHAR

Reporting compositions as atom and weight percent yields both ...

Reporting compositions as atom and weight percent yields both dimensionless quantities but their conceptual interpretation differs. A normalization based on atom_percent counts relative to the total number of atoms which are of a particular type. By contrast, weight_percent normalization factorizes in the respective mass of the elements. Software libraries that work with units, like pint in Python, are challenged by these differences as at.-% and wt.-% are both fractional quantities.

Any of these values: atom_percent | weight_percent

total: (optional) NX_NUMBER (Rank: 1, Dimensions: [n]) {units=NX_UNITLESS}

Total formula mass or number of atoms, depending on the ...

Total formula mass or number of atoms, depending on the normalization stated in the normalization field.

ELEMENT: (optional) NXatom

If this group is used to report the composition of elements from the periodic ...

If this group is used to report the composition of elements from the periodic table, the group should use the chemical symbol of that element. For other case the group name is unconstrained.

amount: (optional) NX_NUMBER (Rank: 1, Dimensions: [n]) {units=NX_UNITLESS}

Count or weight which, when divided by total yields the composition ...

Count or weight which, when divided by total yields the composition of this element, isotope, molecule, or ion.

composition: (optional) NX_FLOAT {units=NX_DIMENSIONLESS}

Composition value for the element/ion referred to under name. ...

Composition value for the element/ion referred to under name. Composition is reported either normalized for atomic or weight percent. The field normalization should be used to communicate this explicitly. Composition should be reported consistently for all instances ELEMENT.

composition_errors: (recommended) NX_FLOAT {units=NX_DIMENSIONLESS}

Magnitude of the standard deviation of the composition.

Hypertext Anchors

List of hypertext anchors for all groups, fields, attributes, and links defined in this class.

NXDL Source:

https://github.com/FAIRmat-NFDI/nexus_definitions/tree/fairmat/base_classes/NXchemical_composition.nxdl.xml