Prismatic layer

These sulfides consist of two types of alternating, mutually non-commensurate layers. One type (Q layers) has pseudotetragonal symmetry and belongs to the PbS or SnS archetype. The other type (H) are octahedral or trigonal prismatic layers. 

In the mixed octahedral/trigonal-prismatic phases two independent transitions occur a high-temperature transition in octahedral layers and a low-temperature transition in trigonal-prismatic layers [613a, 648] ... 

The Th—I distances in -Thh are 3.20 A in the trigonal-prismatic layers and 3.22 A in the trigonal-antiprismatic layers, so that we cannot detect a difference due to localized d electrons in the former and d cations with delocalized electrons in the latter. These Th—I distances are equivalent to those found in Thl4 where they range from 3.13 to 3.29 A. The shortest interlayer I—I contact distance is 4.13 A. 

We adopted the prismatic layer of a bivalve shell as a model for in vitro repairing (Fig. 28). °° The prismatic layer is comprised of calcite prisms elongated in the c axis and an interprismatic organic framework. In the original prismatic layer, calcite polygonal columns 10-50 pm in diameter... 

Fig. 29 SEM images of the original prismatic layer (a,b), the partially etched one (c,d), and the regenerated one (e,f). The left (a,c,e) and right panels (b,d,f) correspond to the top views and cross-sectional images, respectively. The parts O, E, and R with the arrows indicate the original, the etched, and the repaired parts, respectively. Reprinted with permission from Wiley-VCH. °°... 

Farre, B. and Dauphin, Y. (2009) Lipids from the nacreous and prismatic layers of two pteriomorpha mollusc shells. Comp. Biochem. Physiol, 152B, 103-109. 

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