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Electric properties induced moments

The nuclear relaxation (NR) contributions were computed using a finite field approach [73,74]. In this approach one first optimizes the geometry in the presence of a static electric field, maintaining the Eckart conditions. The difference in the static electric properties induced by the field can then be expanded as a power series in the field. Each coefficient in this series is the sum of a static electronic (hyper) polarizability at the equilibrium geometry and a nuclear relaxation term. The terms evaluated in Ref. [61] were the change of the dipole moment up to the third power of the field, and that of the linear polarizability up to the first power ... [Pg.156]

We have shown in this paper the relationships between the fundamental electrical parameters, such as the dipole moment, polarizability and hyperpolarizability, and the conformations of flexible polymers which are manifested in a number of their electrooptic and dielectric properties. These include the Kerr effect, dielectric polarization and saturation, electric field induced light scattering and second harmonic generation. Our experimental and theoretical studies of the Kerr effect show that it is very useful for the characterization of polymer microstructure. Our theoretical studies of the NLDE, EFLS and EFSHG also show that these effects are potentially useful, but there are very few experimental results reported in the literature with which to test the calculations. More experimental studies are needed to further our understanding of the nonlinear electrooptic and dielectric properties of flexible polymers. [Pg.243]

The electrical properties of materials are important for many of the higher technology applications. Measurements can be made using AC and/or DC. The electrical properties are dependent on voltage and frequency. Important electrical properties include dielectric loss, loss factor, dielectric constant, conductivity, relaxation time, induced dipole moment, electrical resistance, power loss, dissipation factor, and electrical breakdown. Electrical properties are related to polymer structure. Most organic polymers are nonconductors, but some are conductors. [Pg.455]

Field forces due to the induced dipole moment of the field have been listed as evidence of nonthermal action of electric fields on biologic systems. However, the effects require fairly large field strengths, frequently above those that give rise to heating or stimulation of excitable tissues. The field forces also depend on the electric properties of the particle considered and its environment. [Pg.126]

But by its charge distribution alone a molecule is, of course, still very roughly characterised. Actually, the charge distribution will be changed under the influence of another molecule. This property of a molecule can very simply be described by introducing a further constant, the polarisability a. In an external electric field of the strength F a molecule of polarisability a shows an induced moment... [Pg.5]

The interaction of light with a molecule can be described by the influence of its eleetric field on the electron density. The eleetric field E acting on the molecule (or material) induces a distortion of the electron density, with (induced) dipole moment / ind (or polarization P on the maeroscopic level). For weak electric fields the magnitude of this induced moment (polarization) can be expected to be linear with the amplitude of the electric field. This linear proportionality suffiees to explain the linear optical properties, e.g., refraction and optical activity. Yet, when the electric... [Pg.3417]

As an example, explicit expressions of /3 can be given in the case of the dipole polarizability of the H atom and for a few simple VdW interactions which depend on the electrical properties of the molecules such as electric dipole moments and polarizabilities (Stone, 1996). As we have already said, these dipole moments, and the higher ones known generally as multipole moments, can be permanent (when they persist in absence of any external field) or induced (when due, temporarily, to the action of an external field and disappear when the field is removed). [Pg.158]

The most traditional experimental determination of p is the electric field-induced second harmonic (EEISH) method, which requires the molecules to be aligned in solution by an electric field, by means of their static dipole moment (po). The EEISH signal is therefore proportional to po and to p <>c (projection of p on po), which is assumed to be equal to p in most cases. The bulk NLO properties are frequently evaluated as the efficiency of a powdered sample in second-harmonic generation (SHG), or as the d components of the x tensor. [Pg.352]

When evaluated, the summation in Eq. (11) is a rank-one polytensor that represents the potential experienced at molecule A in terms of field components, field gradient components, and so on. This can be used with response properties such as shielding polarizabilities to find property changes dues to electrical influence. The evaluation is analogous to Eq. (11). The incorporation of mutual or back polarization/hyperpolarization requires a self-consistent solution for the induced moments, and this can be done iteratively [170] or if there are no hyperpolarizabilities, it can be done by matrix inversion. [Pg.26]

The magnitude and orientation of the induced dipole is a function of the dielectric properties of the particle and the surrounding medium. These induced moments in a nonuniform electric field can create a translational and/or rotational force on a particle. The applied electric field for dielectrophoresis can be either direct current or alternating current (AC), but it is typically the latter of the two. [Pg.573]

Haskopoulos and MarouUs [10] studied the interaction electric properties of H20 Rg (Rg = He, Ne, Ar, Kr, Xe). Correlation effects have been taken into account by employing M0Uer-Plesset (MP2, MP4) and coupled-cluster theories (CCSD, CCSD(T)) in connection with flexible, carefully designed basis sets. Bara-nowska et al. [11] computed the interaction-induced axial static dipole moments, polarizabilities and first hyperpolarizabilities of HCHO (HF)n (n= 1,2). They employed a series of methods (e.g. MP2, CCSD(T)) in connection with various basis sets. [Pg.130]

Electrical Properties. The piezoelectricity of the technologically important polymer of vinylidene fluoride (PVDF) has been the subject of modeling for several decades (see Piezoelectric Polymers). An early example of the use of molecular mechanics to aid in the calculation of the mechanical and electrical properties of this polymer is found in the work of Tadokoro and co-workers (390,391). Subsequent investigation of PVDF by Karasawa and Goddard (83) focussed on the prediction of alternative crystal structures with use of the shell model to captiu-e polarization effects. The latter phenomenon was further explored by Carbeck and co-workers (84), who used the shell model to show that the induced moment because of neighboring dipoles in the crystal increases the dipole per repeat imit by about 50% over its value in the isolated molecule. [Pg.4833]

The structural unit of the copolymer -(-CH2-CF2)n-(-CF2-CHF-)m- contains n and m corresponding monomer links. The ferroelectric properties are attributed to transverse dipole moments, formed by positive hydrogen and negative fluorine atoms. Below the temperature of the ferroelectric phase transition (about 80-100°C), the main chain of the polymer is in all-trans form and the dipole moments are parallel, at least, within ferroelectric domains separated fi-om each other by domain walls. The ferroelectric switching is due to an electric field induced, collective flip-flop of the dipoles around the backbone of the polymer. Several recent studies were devoted to a local ferroelectric switching of the domains in cast P(VDF-TrFE) films [6-8]. To this effect, a powerful technique, called Electrostatic Force Microscopy (EFM) [9] was used which was developed for studies of domains in thin ferroelectric films, see papers [10, 11] and references therein. [Pg.96]


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See also in sourсe #XX -- [ Pg.155 , Pg.158 , Pg.159 , Pg.161 , Pg.198 ]

See also in sourсe #XX -- [ Pg.155 , Pg.158 , Pg.159 , Pg.161 , Pg.198 ]




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