Solid phase, slightly disordered

An active form of the compound, that is, a very fine crystalline precipitate with a disordered lattice, is generally formed incipiently from strongly over-saturated solutions. Such an active precipitate may persist in metastable equilibrium with the solution and may convert ( age ) only slowly into a more stable inactive form. Measurements of the solubility of active forms give solubility products that are higher than those of the inactive forms. Inactive solid phases with ordered crystals are also formed from solutions that are only slightly oversaturated. 

Samples prepared in this way allow a range of morphologies from microcrystalline to amorphous to be obtained. In this review it will be possible to cover only part of the literature describing measurements on such systems. The discussion will, therefore, be limited to three topics, a) the characterization of highly disordered polymers in solution and solid phases, b) photo-currents in slightly disordered solids and c) doping of PDAs to enhance conductivity,... 

Dynamical properties of the commensurate and uniaxial incommensurate phases according to the model of Refs. 232, 340, and 342 could also be explored by the molecular dynamics technique used [203, 352]. It is found that in-plane and out-of-plane motions can be analyzed separately for ori-entationally ordered N2 on graphite [203]. The 40-ps simulations below the orientational ordering transition (see Ref. 342) show [203] that the amplitude of reorientation is small and the out-of-plane motion nearly harmonic in both phases, whereas the in-plane motion is more complex, because it is anhar-monic and collective. The out-of-plane motion in the disordered phases is still harmonic, but more strongly damped, and the in-plane dynamics cannot be analyzed any more in terms of a cumulant expansion. Thus, there is little qualitative difference between the reorientational motion observed in the commensurate and uniaxially compressed solids. Only the out-of-plane motion is slightly less damped in the uniaxial phase, and the fluctuations from the planar configuration are more pronounced. 

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