Crystal structure and charge distribution of pyrazine: effects of extinction, thermal diffuse scattering and series termination
Abstract
<h2>Acta Crystallographica Section B</h2><h3>Structural Crystallography and Crystal Chemistry</h3><h3>0567-7408</h3> <h2>research papers</h2> Volume 32 Part 12 Pages 3178-3185 December 1976 <h2>Crystal structure and charge distribution of pyrazine: effects of extinction, thermal diffuse scattering and series termination</h2> G. de With, S. Harkema and D. Feil 3178 Acta Cryst. (1976). B32, 3178 Crystal Structure and Charge Distribution of Pyrazine: Effects of Extinction, Thermal Diffuse Scattering and Series Termination* BY G. DE WITH, S. HARKEMA AND D. FEIL Chemical Physics Laboratory, Twente University of Technology, P.O. Box 217, Enschede, The Netherlands (Received 26 April 1976; accepted 14 June 1976) The crystal structure and electronic charge distribution of pyrazine (1,4-diazabenzene) has been deter- mined at 184 K by X-ray methods. The structural results of Wheatley [Acta Cryst. (1957), 10, 182-187] have been confirmed. A clear indication of bonding effects is obtained. Neither positional and thermal parameters nor difference-Fourier maps are affected by extinction. The effect of thermal diffuse scattering (TDS) on positional parameters is also negligible. However, after correction for TDS, thermal param- eters increase significantly. The difference-Fourier map is influenced by TDS as well as the inclusion of high-order Fourier terms. Introduction Although the crystal structure of pyrazine (C4H4N2) has been determined quite