Coordinate errors due to rotational oscillations of molecules
Abstract
<h2>Acta Crystallographica</h2><h3></h3><h3>0365-110X</h3> <h2>short communications</h2> Volume 14 Part 8 Pages 896-897 August 1961 <h2>Coordinate errors due to rotational oscillations of molecules</h2> D. W. J. Cruickshank Acta Cryst. (1961). 14, 896 Coordinate errors due to rotational oscillations of molecules. By D. W. J. CRUm~S~A~K, School of Chemistry, The University, .Leeds 2, England (Received 4 April 1961) The writer has shown (Crulckshank, 1956a) how molec- ular angular oscillations can cause the maximum of an atomic peak in the electron density to be displaced towards the centre of rotation. The shift was taken to be in a radial direction and was calculated as /1 = ½r 1 +s2/q---------~ + 1 ' (1) where r is the distance from the centre of molecular oscillation, s2 and t~ are the mean square amplitudes of oscillation of the atom in the rotations about the two principal axes perpendicular to the radius and q~ is the Gaussian-breadth parameter for the peak before the rotational oscillations are considered. The previous derivation assumed that only angular oscillations about axes perpendicular to the radius were relevant, since the atom is not moved by an oscillation about this radius. This assumption is clearly wrong in general. For if there is