SMCPS

SMCPS (Statistical Mechanics for Heat Capacity and Entropy Cp and S) is a Fortran program written by Sheng [74]. This program is useful for users of computational chemistry, such as Gaussian 98 [64], to calculate thermodynamic properties for molecules with hindered rotations. Required input parameters to SMCPS can be extracted from Gaussian98 calculations to determine the desired thermodynamic properties. The thermodynamic properties can then be directly applied to kinetic models, or other systems requiring thermodynamic properties. The program assumes the system of interest is at one atmospheric pressure, where most of literature thermodynamic data are found. 

The statistical mechanics treatment to determine thermodynamic properties for Cp, S and AH(T-0°K), as described above and in Sheng s thesis [74], has been fully implemented. 

The results from SMCPS compare very well with both the NIST [75] and TRC [76] reported 

The maximum number of different temperatures allowed is 40 and the maximum number of frequencies allowed is 500, which is sufficient for 166 atoms, i.e. for most applications (this maximum can be readily expanded). 

Accurate treatment of hindered internal rotators is not included in this program for hindered rotor barriers of 4 kcal mof or less a more accurate treatment is recommended. More accurate methods are available and include those of Pitzer and Gwinn [77], McClurg, et al. [78, 79], Knyazev [80] or Rotator [47]  

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Stereogenic Elements in SmCP Phases SmCP Supermolecular Diastereomers... 

Taken from the three spontaneous symmetry-breaking events leading to this layer structure [formation of layers with long-range orientational order of the director (Sm), tilt of the director from the layer normal (C), and polar orientation of the molecular arrows (P)], we term phases of this type SmCP. All of the complex textures and EO behavior of NOBOW in the B 2 phase can be understood in terms of various stacking modes of SmCP layers as shown in Figure 8.23. 

It is interesting to point out here that with all of the theoretical speculation in the literature about polar order (both ferroelectric and antiferroelectric) in bilayer chevron smectics, and about reflection symmetry breaking by formation of a helical structure in a smectic with anticlinic layer interfaces, the first actual LC structure proven to exhibit spontaneous reflection symmetry breaking, the SmCP structure, was never, to our knowledge, suggested prior to its discovery. 

One of the key experimental results leading to the elucidation of this overall structural puzzle involved depolarized reflected light microscopy (DRLM) studies on NOBOW freely suspended films in the high-temperature SmCP phase.48 In the freely suspended films it appears that only one phase is observed, which is assumed to be the phase forming the majority domains in the EO cells. The DRLM experiment provides two key results. First, thin films of any layer number have a uniformly tilted optic axis, suggesting all of the layer interfaces are synclinic. Second, films of even-layer number are nonpolar, while films of odd-layer number are polar, with the polar axis oriented normal to the plane of the director tilt (lateral polarization). 

The layer stacking is synclinic in the tilt plane and antiferroelectric in the polar plane. The phase composed of an infinite number of SmCP layers stacked in this way is termed SmCsP, where the subscripts S and A each refer a structural feature of the layer interfaces between adjacent pairs of layers. If two adjacent layers are tilted in the same direction, the interface is synclinic (subscript S) in the tilt plane. If two adjacent layers have antiparallel orientation of their polar axes, then the layer interface is said to be antiferroelectric (A) in the polar plane. 

Figure 8.26 Illustration of supermolecular structure and pairwise relationships for isomeric SmCP phases is given.

A,A -Dianionic fused six-membered heterocyclic ligands derived from phenazine and quinoxaline have been found in Ln complexes including [(SmCp )2(p-ri ri -Ci2HgN2)]... 

A close look at the hydrogenolysis reaction of the Cp2 SmCH(TMS)2 complex with H2Si(SiMe3)2 shows that the two compounds do not react directly. The kinetic profile shows an S-shape form with an induction time. This shape is consistent with a second-order autocatalytic mechanism in which the reaction is catalyzed by a product or an intermediate. Indeed, the induction period was completely eliminated by addition of catalytic amounts of H2, [Cp2 SmH]2, or of the complex [Cp2 Sm (p-H) (p-C CsMe SmCp ], which is a decomposition product of the [Cp2 SmH]2. Thus, two possible mechanistic pathways (Schemes 3 and 4) have been proposed to explain the hydrogenolysis reaction. 

Supramolecular chemistry can be used to create the bent cores that give rise to the symmetry breaking in this family of liquid crystals [139]. The formation of a complex between a calamitic benzoic acid derivative and a bent core terminated with a pyridyl group—neither of which display mesomorphic behaviour—gave rise to a material which displayed SmCP mesophases. The achiral bent cores can also give rise to symmetry breaking when they are attached to flexible polymeric chains, such as poly(siloxane) [140]. 

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