Acta Crystallographica Section A

Foundations of Crystallography

Volume 62, Part 1 (January 2006)

research papers

Acta Cryst. (2006). A62, 1-10 [ doi:10.1107/S0108767305036111 ]

X-ray diffraction by a crystal in a permanent external electric field: electric-field-induced structural response in -GaPO₄

S. Gorfman, V. Tsirelson, A. Pucher, W. Morgenroth and U. Pietsch

Abstract: For the first time, site-selective distortion has been investigated for two different structural units in the ternary compound [alpha] -GaPO₄ under the influence of a permanent external electric field. Based on 54 measured reflection intensities, the electric-field-induced distortion of PO₄ and GaO₄ tetrahedra in [alpha] -GaPO₄ crystals is evaluated using a model of pseudoatomic displacements introduced recently [Gorfman, Tsirelson & Pietsch (2005). Acta Cryst. A61, 387-396]. A stronger variation of the P-O bond lengths in the PO₄ tetrahedron was found compared to the bonds in the GaO₄ tetrahedron. The different distortions of the tetrahedra owing to the electric field were analysed in terms of the valence charge density of [alpha] -GaPO₄ and its topological characteristics. The larger charge of the P pseudoatom compared to the Ga atom was recognized as the main reason for the higher sensitivity of the PO₄ tetrahedron to a permanent external electric field.

Keywords: external electric field; -GaPO₄; pseudoatomic displacements.


	Portable Document Format (PDF) file (30.6 kbytes) [ doi:10.1107/S0108767305036111/sh5033sup1.pdf ] Summary of experimental data

	Portable Document Format (PDF) file (28.4 kbytes) [ doi:10.1107/S0108767305036111/sh5033sup2.pdf ] Observed and modelled relative variations

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