Chiral dielectric function

Optical Conductivity Optical Dielectric Function Discussion of Conductivity and Dielectric Functions Microwave Frequency Dielectric Constant Pseudoprotonic Add Doping of Polyanihne Comparison of Doped Aniline Tetramers, Aniline Octamers, and Polyanihne Chiral Metalhc-Doped Polyanihne... 

A wide variety of molecular properties can be accurately obtained with ADF. The time-dependent DFT implementation " yields UV/Vis spectra (singlet and triplet excitation energies, as well as oscillator strengths), frequency-dependent (hyper)polarizabilities (nonlinear optics), Raman intensities, and van der Waals dispersion coefficients. Rotatory strengths and optical rotatory dispersion (optical properties of chiral molecules ), as well as frequency-dependent dielectric functions for periodic structures, have been implemented as well. NMR chemical shifts and spin-spin couplingsESR (EPR) f-tensors, magnetic and electric hyperfme tensors are available, as well as more standard properties like IR frequencies and intensities, and multipole moments. Relativistic effects (ZORA and spin-orbit coupling) can be included for most properties. 

Liquid crystals are anisotropic fluids with optical properties similar to those of bire-fringent crystals. They are often inhomogeneous and, as a consequence, the dielectric tensor is a function of position. The inhomogeneity may be a property of the phase, such as the helical structure of chiral phases, or it may be the result of deformations. 

In the standard description of the dielectric properties of the chiral tilted smectics worked out by Carlssonet al. [152], four independent modes are predicted. In the smectic C the collective excitations are the soft mode and the Goldstone mode. In the SmA phase the only collective relaxation is the soft mode. Two high frequency modes are connected to noncollective fluctuations of the polarization predicted by the theory. These two modes become a single noncollective mode in the smectic A phase. There is no consensus [153] as yet as to whether these polarization modes really exist. Investigations of the temperature dependence of the relaxation frequency for the rotation around the long axis show that it is a single Cole-Cole relaxation on both sides of the phase transition between smectic A and smectic C [154]. The distribution parameter a of the Cole-Cole function is temperature-dependent and increases linearly (a=a-pT+bj) with temperature. The proportionality constant uj increases abruptly at the smectic A to SmC transition. This fact points to the complexity of the relaxations in the smectic C phase. 

Fig. 4.9. Ferroelectric Goldstone and soft modes in the chiral smectic phase, (a) Temperature dependence of the relaxation rate /c (b) the dielectric loss spectrum as a function of bias d.c. voltage. (From Ref. 42, with permission.)...

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