ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Rotation and translation functions in reciprocal space, commonly used to find the orientation of a known molecular fragment and/or its position in the unit cell, are all identical or closely related to the function Q(R,t) = 〈|Eh|2|Ehp(R,t)|2〉h, where |Eh| is the observed normalized structure factor and Ehp(R,t) is the normalized structure factor for the partial structure, calculated for orientation R and position t. In this paper, this function is derived from statistical considerations without referring to a Patterson synthesis. From the centrosymmetric and noncentrosymmetric probability density functions, Q(R,t) = 1 + 2p2 and Q(R,t) = 1 + p2 are obtained, respectively, where p2 is the fraction of atoms (scattering power) that has been placed in the correct orientation and position in the unit cell. Alternative search functions, for instance using |Eh|4 instead of |Eh|2, are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739481000909
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