Molrefraktion von Ionen und Molek�len im Lichte der Atomstruktur

Fajans, K.; Joos, Georg

doi:10.1007/bf01327574

Cited by 356 publications

(67 citation statements)

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“…Solvent effects were introduced nonexplicitly by means of the COSMO model. 59,60 The values of the atomic radii correspond to the Van der Waals radii derived by Klamt. 59,60 For Cs, a value of 3.205Å was used.…”

Section: Methodsmentioning

confidence: 99%

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Electronic and relativistic contributions to ion-pairing in polyoxometalate model systems

Sures

Serapian

Kozma

et al. 2017

Phys. Chem. Chem. Phys.

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Ion pairs and solubility related to ion-pairing in water influence many processes in nature and in synthesis including efficient drug delivery, contaminant transport in the environment, and self-assembly of materials in water. Ion pairs are difficult to observe spectroscopically because they generally do not persist unless extreme solution conditions are applied. Here we demonstrate two advanced techniques coupled with computational studies that quantify the persistence of ion-pairs in simple solutions and offer explanations for observed solubility trends. The system of study, (TMA,Cs)

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Section: Methodsmentioning

confidence: 99%

“…59,60 The values of the atomic radii correspond to the Van der Waals radii derived by Klamt. 59,60 For Cs, a value of 3.205Å was used. Input and output files for all of the above calculations are entirely available on-line, within the ioChem-BD repository.…”

Section: Methodsmentioning

confidence: 99%

Electronic and relativistic contributions to ion-pairing in polyoxometalate model systems

Sures

Serapian

Kozma

et al. 2017

Phys. Chem. Chem. Phys.

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“…By applying their method to a great number of crystals, they obtained a list of polarizability values of ions. TK & S polarizability values differ considerably from polarizability values that have been otherwise determined (Pauling, 1927;Born & Heisenberg, 1924;Mayer & Goeppert-Mayer, 1933;Fajans & Joos, 1924;Langhoff, 1965;Cohen, 1965Cohen, , 1966Lahiri & Mukherji, 1967). The cation polarizabilities are generally higher, and the anion polarizabilities lower, than those obtained by other methods for gaseous ions.…”

Section: Introductionmentioning

confidence: 64%

“…Table 3 lists some polarizabilities calculated by theoretical methods together with polarizabilities determined by Pauling (1927), Mayer & Goeppert-Mayer (1933), Fajans & Joos (1924) I thank the Deutsche Forschungsgemeinschaft for financial support and the Rechenzentrum der Universit,it Hamburg and the DESY-Rechenzentrum, Hamburg for computer time.…”

Section: (Iv) Comparison With Other Investigationsmentioning

confidence: 99%

Electronic polarizabilities of ions in doubly refracting crystals

Pohl¹

1978

Acta Cryst Sect A

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A method is described for determining electronic polarizabilities of ions in doubly refracting ionic crystals solely from crystal data. An expression for computing polarizabilities by a least-squares fit can be derived. Such a method is used to obtain values for the polarizability of cations for the sodium D line in A3: Na ÷ 1.7, K + 11.6, Rb + 19.1, TI + 48.7, Ca 2+ 5.2, Sr 2+ 11.1, Ba 2÷ 23.2, Pb 2÷ 38.3. Evidence is given of decreasing polarizability of the 02-ion in aragonite-type carbonates with decreasing cation sizes.

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“…There are however additional difficulties with every improved model, leading to the conclusion that the problem of too many coefficients and not enough data cannot be easily removed. As pointed out by a number of authors (Spangenberg, 1923;Fajans & Joos, 1924;Born & Heisenberg, 1924;Bragg, 1925;Batsanov, 1966;Pohl, 1978;Pohl, Eck & Klaska, 1978) the polarizability of the anions varies with the size of the cation. Specifically, small cations tend to reduce the polarizability of the anions.…”

mentioning

confidence: 99%

Point-dipole theory and optical birefringence of calcite-type carbonates

Pohl¹,

Ram²

1979

Acta Cryst Sect A

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A critical survey of the literature has revealed that recent structure determinations and optical data are available for only three calcite-type carbonates: calcite, rhodochrosite and magnesite. For these structures, the limitations of the pointdipole approximation are discussed.The point-dipole model was introduced by Bragg (1924) to explain quantitatively the birefringence of calcite and aragonite with respect to the crystal structures. In this approach optical anisotropy arises from differences in dipole-dipole coupling along different crystallographic directions. This source of anisotropy is connected with the Lorentz-factor tensor. In addition, however, optical anisotropy may arise from an intrinsic anisotropy in the constituent ions. In this case electronic polarizability tensors should be considered.In order to investigate the relation between atomic arrangement and double refraction, the crystals of carbonates have been used repeatedly. The latest studies are those given by Isherwood &James (1976) andPohl (1978). In his paper Pohl (1978) has developed a method to determine the electronic polarizabilities of ions from structural and optical data by a least-squares fit. The method is based on Bragg's (1924) model of point dipoles and on an exact calculation of Lorentz-factor tensors. This model satisfactorily accounts for the double refraction of aragonite-type carbonates. In the present paper we discuss the application of the method to calcite-type carbonates.Structural parameters of only three calcite-type carbonates have been determined: calcite (Chessin, Hamilton & Post, 1965), rhodochrosite (Brown & Forsyth, 1967) and magnesite (Oh, Morikawa, Iwai & Aoki, 1973). Optical constants are given by Winchell & Winchell (1964). Application of Pohl's (1978) method yields the electronic polariz- Bragg's (1924) ideas, the birefringence arises from the oxygens within the isolated COl-groups: the stronger the birefringence the stronger the influence of the O z-ions on each other. Strengthening of the oxygen interaction can take place in two ways. Firstly, the distance between the carbon and oxygen can be diminished. Secondly, the polarizability of the oxygen ion can be increased. Since the C-O distance is fixed according to the structure determination, only an increased polarizability of the 0 2-ion remains. However, this results in an increased mean refractivity which in return is compensated by a smaller polarizability of the cation, thus explaining the above results.To overcome the shortcomings encountered with the Bragg model of point dipoles, two improvements may be considered. Firstly, the point dipoles can be positioned outside the atomic centers, because the outer electrons responsible for the optical effects may have a center of gravity distinct from that determined by X-rays. Secondly, an intrinsic anisotropy can be allocated to the polarizability of the ions. Both of these improvements involve the introcluction of at least one extra parameter. Thus the number of adjustable parameters will exce...

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Molrefraktion von Ionen und Molek�len im Lichte der Atomstruktur

Cited by 356 publications

References 0 publications

Electronic and relativistic contributions to ion-pairing in polyoxometalate model systems

Electronic and relativistic contributions to ion-pairing in polyoxometalate model systems

Electronic polarizabilities of ions in doubly refracting crystals

Point-dipole theory and optical birefringence of calcite-type carbonates

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