Piezoelectric coefficients of mNA organic nonlinear optical material usingsynchrotron X-ray multiple diffraction

Distortions produced in the unit cell of a nonlinear organic crystal under the influence of an applied electric field E are investigated by using sync hrotron x-ray multiple diffraction (MD). A typical MD pattern shows numerou s (hkl) secondary peaks and the position of each one is basically a functio n of the unit cell lattice parameters. Thus small changes in any parameter due to a strain produced by E give rise to a corresponding variation in the (hkl) peak position. The method was applied to the meta-nitroaniline (mNA) crystal and we were able to determine three piezoelectric coefficients. [S 0031-9007(98)07912-5].