ISSN:
1600-5767
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Geosciences
,
Physics
Notes:
It is shown that in fixing the crossed Nicols positions a systematic error must invariably be introduced caused by the parasitic ellipticities of the polarizer and analyzer and the refraction of the light beam by the specimen. A method has been derived by which this systematic error can be removed from the original HAUP method. The improved method has been successfully applied to the measurement of the temperature dependence of the gyration-tensor component g23 of [N(CH3)4]2ZnCl4, although it is as small as 10−7. The study of optical activity shows directly that the order parameter of the incommensurate phase of the (NH4)2SO4 family is complex and that a phason exists in this phase. It can be shown that the optical activity of the incommensurate phases can be classified into three types, [N(CH3)4]2ZnCl4 corresponding to the case where the nearly commensurate domains are optically active. The extensive usefulness of optical activity to the study of phase transitions is suggested.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0021889886089197
