Accession Number : AD0615068

Title :   THERMAL EXPANSION AND STACKING DISORDER IN MOLECULAR CRYSTALS. I. 2,2'-PYRIDIL (DILATACION TERMICA Y DESORDEN DE APILAMIENTO EN CRISTALES MOLECULARES. I. 2,2'-PIRIDIL,

Corporate Author : MADRID UNIV (SPAIN)

Personal Author(s) : Felix,A. ; Canut,M. L. ; Amoros,J. L.

Report Date : 1964

Pagination or Media Count : 11

Abstract : The thermal expansion quadric of 2,2'-pyridil (D1-2pyridyl glyoxal) was determined by Weisenberg method, between-175 and 20C. The monoclinic crystal shows the maximum and minimum expansion in the plane (010). Although the bond system does not involve other bonds but van der Waals forces, the thermal expansion coefficients are smaller than the expected. 2,2'-pyridil is formed by curled sheets of molecules formed by chains of molecules along (101). This causes some possibility of stacking lines along rows of l = 1 (from 011 to 021) and l = 3 (from 013 to 043) which were detected in Weissenberg and Laue photographs of some single crystals. A two dimensional statistical model where stacking disorder along (001) of the layers of molecules has been introduced gives a Fraunhofer pattern showing general agreement with the x-ray experiments. Both ordered and disordered crystals can be obtain from a solution of the substance in ethanol. (Author)

Descriptors :   (*NITROGEN HETEROCYCLIC COMPOUNDS, CRYSTALLOGRAPHY), (*CRYSTAL DEFECTS, NITROGEN HETEROCYCLIC COMPOUNDS), (*THERMAL EXPANSION, NITROGEN HETEROCYCLIC COMPOUNDS), ALDEHYDES, CHEMICAL BONDS, MOLECULAR ASSOCIATION, X RAY DIFFRACTION, SPAIN

Distribution Statement : APPROVED FOR PUBLIC RELEASE