Difference between revisions of "Direct methods"
From Online Dictionary of Crystallography
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<font color="blue">Méthodes directes</font> (''Fr''). <Font color="black"> Metodi diretti </Font>(''It''). <font color="purple">直接法</font> (''Ja''). | <font color="blue">Méthodes directes</font> (''Fr''). <Font color="black"> Metodi diretti </Font>(''It''). <font color="purple">直接法</font> (''Ja''). | ||
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The family of methods for solving the [[phase problem]] in crystal [[structure determination]]. The phases of scattered diffraction beams cannot be directly observed. However, they can be estimated from probability relationships applied to the phases of the most intense diffraction peaks. The facts that scattering centres in a crystal are discrete atoms (''i.e.'' sources of electron density) and that the electron density must be non-negative are the types of constraints that restrict the possible values of the phases, and allow initial estimates of some of them. | The family of methods for solving the [[phase problem]] in crystal [[structure determination]]. The phases of scattered diffraction beams cannot be directly observed. However, they can be estimated from probability relationships applied to the phases of the most intense diffraction peaks. The facts that scattering centres in a crystal are discrete atoms (''i.e.'' sources of electron density) and that the electron density must be non-negative are the types of constraints that restrict the possible values of the phases, and allow initial estimates of some of them. | ||
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== See also == | == See also == | ||
Revision as of 12:03, 6 February 2012
Méthodes directes (Fr). Metodi diretti (It). 直接法 (Ja).
Definition
The family of methods for solving the phase problem in crystal structure determination. The phases of scattered diffraction beams cannot be directly observed. However, they can be estimated from probability relationships applied to the phases of the most intense diffraction peaks. The facts that scattering centres in a crystal are discrete atoms (i.e. sources of electron density) and that the electron density must be non-negative are the types of constraints that restrict the possible values of the phases, and allow initial estimates of some of them.
See also
Direct methods. C. Giacovazzo. International Tables for Crystallography (2006). Vol. B, ch. 2.2, pp. 210-234 doi:10.1107/97809553602060000555