ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The molecular reorientation induced by an external electric field has been determined for the first time in order to obtain a microscopic understanding of the interaction between crystals and electric fields. Changes in scattering intensity are found when an electric field is applied parallel to the polar axis of a non-linear optical crystal of 2-methyl-4-nitroaniline (MNA), which has large piezoelectric constants [Paturle, Graafsma, Sheu, Coppens & Becker (1991). Phys. Rev. B, 43, 14683–14691]. The effect has been analyzed in terms of a change in cell parameters, a molecular rotation of 0.45 (5) × 10−2° about an axis nearly parallel to the electric field and a molecular translation of 0.19 (3) × 10−3] Å along the b axis. Since the orientation of the molecular dipole moment vector is unaffected, the piezoelectric contribution to the permittivity for this electric field direction is small. As expected, the centrosymmetric crystals of p-nitroaniline and p-nitropyridine N-oxide have no first-order converse piezoelectric effect and show no measurable change in X-ray scattering intensity under the influence of an external electric field of 2.2 × 106 V m−1. For the non-centrosymmetric crystals of 3-methyl-4-nitropyridine N-oxide, the effect is small, in agreement with the small value of the piezoelectric constants.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108767391008887
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