L. Becka, D. Cruickshank
Jun 11, 1963
Citations
2
Influential Citations
71
Citations
Quality indicators
Journal
Proceedings of the Royal Society of London. Series A. Mathematical and Physical Sciences
Abstract
On account of its cubic molecular and crystal symmetry, hexamethylenetetramine is a key substance in the study of the lattice vibrations of molecular crystals; its anisotropic atomic-vibration amplitudes have been determined at 298, 100 and 34 °K from three-dimensional single crystal X-ray data. Two independent sets of experiments were done with Cu and Mo radiation; these led to results in very close agreement with one another (and with results derived from previous X-ray and neutron data at room temperature). Typical final discrepancy factors obtained from full-matrix least-squares refinements are 3.4 % for 95 Mo reflexions and 6.3 % for 44 Cu reflexions at 34 °K. The studies at the three temperatures provide direct support for the rotational-oscillation correction for atomic co-ordinates. The corrected weighted-mean dimensions from eight determinations are C—N = 1.476 ± 0.002 Å, ∠N—C—N = 113.6 ± 0.2°, ∠C—N—C = 107.2 ± 0.1°, and from the neutron study C—H = 1.088 ± 0.011 Å. The compact arrangement of molecules in the crystal is described.