Polarisability definition

The values of Sp also behave systematically, as shown in Fig. 21, in which 5p is plotted against k for the various series B XY. It is evident that, for a given XY, Sp is an approximately linear function of k and hence of the strength of the interaction. Moreover, for a given B the order of 5p is IC1 > BrCl Br2 > CI2, which is the order of the polarisabilities of the leading atoms X in B XY and therefore seems reasonable from the definition (see earlier) of 5p. 

On the whole ternary fluorides of the bivalent transition metals are least affected by polarisation. This is partly the reason why in the fluoro-perovskites Goldschmidt s tolerance relation is much more definite, than... 

The polarimeter consists of two Nicol prisms N and Nx (Fig. 43) set at a distance from one another and on a common axis. Nx is the polariser and N the analyser. The polarimeter tube T, containing a definite... 

In practice, observations are made easier and more exact by the introduction into the polariser of arrangements and devices such that the field visible through the eye-piece is divided into two or more zones, these being equally illuminated only for a definite position of the analyser. This position is easy to fix exactly, since the line of separation of the zones is then scarcely visible, whereas a slight displacement causes the immediate appearance of the contrast between the differently illuminated zones. Such position is taken as the standard, and since in it there is neither darkness nor a maximum of light, the apparatus is known as a half-shadow polarimeter. 

There have been many attempts to formulate a procedure to correct for BSSE and both a posteriori and a priori schemes are available [4]. The counterpoise approach (CP) [5], based on the use of "ghost orbitals , is the most common a posteriori procedure. Nevertheless, the addition of the partner s functions or ghost orbitals to counterbalance the BSSE does not provide a definite solution to the problem [6]. The introduction of the "secondary superposition error", upsetting the multipole moments and polarisabilities of the... 

Definition of molecular mass averages, 17 Deformation flexural, 825 plastic, 830 polarisation, 325 properties, 824 uniaxial, 825 De Gennes... 

Despite the success in parameterizing acid/base and many other properties for a range of different compounds, it is obvious that the simple electrostatic model used by Taft and extended by others [27, 28] have fundamental weaknesses - both with regards to the domain of validity and at a more fundamental level. The model is more intuitive than physical, in the sense that the inductive effect, polarisation effect, resonance effect, mesomeric effect and steric effect have no proper quantum mechanical definition, and can therefore not be derived directly from the system s wave function [29,30]. 

The fust term on the right-hand side, eqe Eq, represents the instantaneous response of the material to the field. The second term, o( s — Eoo O Oj represents the slower contribution from polarisation of dipoles, with the factor F(t) describing the time development of the underlying orientation process. By this definition T(0) = 0 and f (oo) = 1. We further assume that the rates at which dipolar polarisation DP(t) progresses towards its equilibrium value DP(oo) = e0(es - oo)Eq is proportional to its degree of departure from equilibrium, i.e. 

The power of the solvation equation approach is that it can characterise various partition systems and lipophilicity scales by five molecular descriptors (dispersivity, size, polarisability-dipolarity, H-bond acidity and basicity). All of the five descriptors should be included into the linear regression equations by definition. When one or two coefficients are not significantly different from zero, it means that that particular property does not play a significant role in the partition. 

Ryss, Yu.S., 1969. The contact polarisation curve (CPC) technique for definition of mineral composition and size of ore bodies. In Principles and Techniques of Exploration. Rotaprint VITR, N65 34-42 (in Russian). 

Fig. 1. Experimental set up (90° collection optics) for the measurement of laser Raman scattering, illustrating the definition of the depolarisation ratio. ly and Ij are the intensities of light scattered, respectively, parallel and perpendicular to the polarisation of the incident exciting beam...

The definition of the depolarisation ratio, pi, is illustrated in Fig. 1 for linearly-polarised incident radiation and a 90° scattering geometry. In the normal Raman effect it is well known that the measurement of p may identify the symmetry of the vibrational mode responsible for a given Raman band pi < 3/4 (pi = 0 in cubic or higher symmetries) for totally symmetric modes and Pi= 3/4 for non-totally symmetric modes. In the resonance Raman effect, the value of P, and its dependence on the exciting frequency, may be more informative. This is because the symmetries of... 

In the seventies, most of the 37 papers (8-24) that we report are quantum chemical calculations, mainly on H502+ (8-14,20) or H30+(14-20) and a few on larger clusters with n=4-6 (8,9). However these last calculations are not accurate, obtained either from semi-empirical methods (8) or with small basis sets (DZ, 4-31G) and at the SCF level in ab initio calculations (9). The first accurate Cl calculations definitely establish the pyramidal geometry of the oxonium ion (15,16). The first ab initio determination of the barrier in H502+ appeared in 1970 (10). An attempt was made to study the effect of Cl on this barrier (11) and the abnormal polarizability of H502+ (12). At the end of this decade appeared the first Cl ab initio calculation on the excited states of H30+ (19) and the first CNDO calculations on excited states of larger clusters (20). In parallel to these quantum chemistry studies, a kinetic model (21) treats large systems with n=20 and 26, a polarisation model (22) is proposed, and a study on the liquid uses a continuum model (23). 

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