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In a homogeneous cell the origin of the steep decrease, which is always observed in the liquid crystal tilt angle on an SiO coating as a function of temperature in the range close to Tc, is traced back to the growth of twist domains. It appears that a magnetic null method is unsuited for accurate tilt angle measurements in the relevant temperature region, because it is based on the assumption of a homogeneous director pattern in the sample cell.
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Sprang et al. (1983) studied this question.
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