Difference between revisions of "Incommensurate composite crystal"
From Online Dictionary of Crystallography
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<Font color="blue">Cristal composite</font> (Fr.) | <Font color="blue">Cristal composite</font> (Fr.) | ||
| − | + | == Definition == | |
An ''incommensurate composite crystal'' is a compound with two or more (''N'') subsystems that are | An ''incommensurate composite crystal'' is a compound with two or more (''N'') subsystems that are | ||
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''n'' is the rank of the vector module. | ''n'' is the rank of the vector module. | ||
| − | + | == Applications == | |
Examples are intergrowth crystals and adsorbed monolayers. To the former belongs | Examples are intergrowth crystals and adsorbed monolayers. To the former belongs | ||
Revision as of 15:20, 30 June 2010
Incommensurate Composite Crystal
Cristal composite (Fr.)
Definition
An incommensurate composite crystal is a compound with two or more (N) subsystems that are themselves modulated structures, with basis structures that are mutually incommensurate. Each subsystem (numbered by ν) has a reciprocal lattice for its basic structure with three basis vectors [math]a_i^{*\nu}[/math]. There is a basis of the vector module of diffraction spots that has at most 3N basis vectors [math]A_j^*[/math] such that
[math] a_i^{*\nu}~=~\sum_{j=1}^n Z_{ij}^{\nu} A_j^* ~~~(i=1,2,3),[/math]
where [math]Z_{ij}^{\nu}[/math] are integer coefficients. If n is larger than the dimension of space (three), the composite crystal is an aperiodic crystal. n is the rank of the vector module.
Applications
Examples are intergrowth crystals and adsorbed monolayers. To the former belongs Hg3-δAsF6 with two systems of Hg chains inside the host lattice formed by AsF6 octahedra. Another example is nonadecane in the channels of a urea host crystal.