Acta Crystallographica Section B

Structural Science

Volume 58, Part 4 (August 2002)

research papers

Acta Cryst. (2002). B58, 728-733 [ doi:10.1107/S0108768102004263 ]

Structural characterization of crystals of -glycine during anomalous electrical behaviour

P. Langan, S. A. Mason, D. Myles and B. P. Schoenborn

Abstract: The crystal structure of [alpha] -glycine has been investigated in the temperature range 288-427 K using neutron diffraction. The molecular structure does not change significantly and the putative crystallographic phase transition associated with anomalous electrical behaviour in this temperature range is not observed. The unit cell expands anisotropically with increasing temperature, with the unique monoclinic b axis, corresponding to the stacking direction of molecular layers, changing the most. The increasing separation of antiferroelectric molecular layers with increasing temperature is driven by an increase in molecular libration about an axis that lies perpendicular to the b axis. There is also a weakening of the interlayer hydrogen bonds with temperature. These structural and dynamic changes will affect the response of molecular dipoles to an applied electric field and provide a possible mechanism for the anomalous electrical behaviour.

Keywords: glycine; amino acids; electrical properties; hydrogen bonding; neutron diffraction; temperature dependence.


	Structure factor file (CIF format) (43.1 kbytes) Contains datablock 288K

	Structure factor file (CIF format) (31.4 kbytes) Contains datablock {vcif WARNING: Line 0: length exceeds internal buffer size (1024) - rest discarded}

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	Structure factor file (CIF format) (31.4 kbytes) Contains datablock {vcif WARNING: Line 0: length exceeds internal buffer size (1024) - rest discarded}

	Structure factor file (CIF format) (12.0 kbytes) Contains datablock {vcif WARNING: Line 0: length exceeds internal buffer size (1024) - rest discarded}

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