Antiferroelectric short-range order

The main effect of a central longitudinal dipole moment in SC and GB molecules is to stabilize smectic layering relative to the nematic phase, when compared with the nonpolar case, due to favourable antiferroelectric short range order [225,227,228]. As the strength of the dipole increases the nematic... 

In this work we focus on the short range order in ferroelastic lead phosphate, Pb3(P04)2, in Sr-doped lead phosphate crystals, in antiferroelectric titanite, CaTiSiOs, and isosymmetric effects in malayaite, CaSnSiOs. 

Evidence in favor of dynamic disorder in a-CO was also obtained from nuclear quadrupole resonance studies [199, 369] and from dielectric measurements [251], which also indicate short-range antiferroelectric order [251]. The rate of molecular reorientation leading to head-tail flips was found to become vanishingly small at low temperatures A head-tail reorientation time of about 5 X lO hours was estimated [369] at a temperature of 10 K. Thus, the extremely slow kinetics at the low temperatures which are energetically necessary to allow for head-tail ordering seems to prevent head-tail ordering in the bulk CO phase. 

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