Absolute sign of piezoelectric d₃₃ and pyroelectric p₃ coefficients in LiClO₄.3H₂O.

The sense of the piezoelectric d₃₃ and the pyroelectric p₃ coefficients for LiClO₄.3H₂O crystals in point group 6 mm has been related to the absolute polarity and atomic arrangement, with the use of anomalous X-ray scattering techniques. The magnitude of d₃₃ is about 4 × 10^-12 CN^-1, that of p₃ about 3.9 × 10^-6 Cm^-2 K^-1. The absolute sense of the spontaneous polarization P_s is calculated to be antiparallel to the positive c-axis direction. The sense of p₃ is negative indicating that the Li⁺ ions become more deeply embedded in the nearest layers of ClO₄^- ions, and that |P_s| increases, with increasing temperature. The sense of d₃₃ is positive, indicating that the Li⁺ ions become displaced further from the ClO₄^- ion layer under tensile stress.