Electron density distribution analysi

J. P. Ritchie,/. Ant. Ghent. Soc., 107,1829 (1985). Electron Density Distribution Analysis for Nitromethane, Nitromethide, and Nitraraide. 

Iversen, B.B., Larsen, F.K., Figgis, B.N. and Reynolds, P.A. (1997) X-N study ofthe electron density distribution in tra s-tetraammine-dinitronickel(II) at 9K transition metal bonding and topological analysis, J. Chem. Soc., Dalton Trans. 2227-2240. 

Yamamoto, K., Takahashi, Y., Ohshima, K., Okamura, F.P. and Yukino, K. (1996) MEM analysis of electron-density distributions for silicon and diamond using short-wavelength X-rays (WKa, ), Acta Cryst., A52,606-613. 

In representations of electron densities, the presence or lack of boundaries plays a crucial role. A quantum mechanically valid electron density distribution of a molecule cannot have boundaries, nevertheless, artificial electron density representations with actual boundaries provide useful tools of analysis. For these reasons, among the manifold representations of molecular electron densities, manifolds with boundaries play a special role. 

The definition of the radius of an ion in a crystal as the distance along the bond to the point of minimum electron density is identical with the definition of the radius of an atom in a crystal or molecule that we discuss in the analysis of electron density distributions in Chapter 6. The radius defined in this way does not depend on any assumption about whether the bond is ionic or covalent and is therefore applicable to any atom in a molecule or crystal independently of the covalent or ionic nature of the bond, but it is not constant from one molecule or crystal to another. The almost perfectly circular form of the contours in Figure... 

Thus there are five bonding electrons giving a bond order of 2.5, consistent with the bond length of 115 pm, versus 121 pm for the four-electron bond in O2 and 110 pm for the six-electron bond in N2. For these and other related molecules, the double-quartet model is a convenient and useful alternative to the conventional molecular orbital model. Moreover, it shows that for a singly bonded terminal atom such as F or Cl there is a ring of six nonbonding electrons rather than three separate lone pairs. As we will see in Chapters 7 and 8, this conclusion is confirmed by the analysis of electron density distributions. 

In the following chapter we show how the topology of an important function of p, the Laplacian, enables us to obtain additional information from the analysis of the electron density distribution. 

This chapter is based on the VSEPR and LCP models described in Chapters 4 and 5 and on the analysis of electron density distributions by the AIM theory discussed in Chapters 6 and 7. As we have seen, AIM gives us a method for obtaining the properties of atoms in molecules. Throughout the history of chemistry, as we have discussed in earlier chapters, most attention has been focused on the bonds rather than on the atoms in a molecule. In this chapter we will see how we can relate the properties of bonds, such as length and strength, to the quantities we can obtain from AIM. 

Gillespie, R.J. (2000). Improving our understanding of molecular geometry and the VSEPR model through the ligand close-packing model and the analysis of electron density distributions. 

Chapters 8 and 9 are devoted to a discussion of applications of the VSEPR and LCP models, the analysis of electron density distributions to the understanding of the bonding and geometry of molecules of the main group elements, and on the relationship of these models and theories to orbital models. Chapter 8 deals with molecules of the elements of period 2 and Chapter 9 with the molecules of the main group elements of period 3 and beyond. 

Contents Introduction. - X-Ray Difraction. -Conformational Analysis. - Structure and Isomerism of Optically Active Complexes. - Electron-Density Distribution in Transition Metal Complexes. - Circular Dichroism. - References. 

The crystallinity of organic pigment powders makes X-ray diffraction analysis the single most important technique to determine crystal modifications. The reflexions that are recorded at various angles from the direction of the incident beam are a function of the unit cell dimensions and are expected to reflect the symmetry and the geometry of the crystal lattice. The intensity of the reflected beam, on the other hand, is largely controlled by the content of the unit cell in other words, since it is indicative of the structural amplitudes and parameters and the electron density distribution, it provides the basis for true structural determination [32],... 

Although successful attempts have been reported on electron density distribution measurements by electron diffraction and other extensions of the tech-nique its principal application has remained the determination of molecular geometry and intramolecular motion. To increase accuracy and to extend stmctural information for more complicated molecules, the most promising recent development is the combined analysis of diffraction and spectroscopic data. The studies of Kuchitsu, cf. have to be mentioned here, followed by an increasing number of investigations by others. 

Hansen, N. K., Study of the Electron Density Distribution in Molecular Crystals by Analysis of X-ray Diffraction Data Using Non-Spherically Symmetric Scattering Functions, Thesis, University of Arhus, Denmark (1978). 

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