Point-charge crystal

Figure 4. Calculated HAB values as a function of Fe -Fe separation, based on the structural model given in Figure 1 and the diabatic wavefunctions I/a and f/B. Curves 1 and 2 are based on separate models in which the inner-shell ligands are represented, respectively, by a point charge crystal field model [Fe(H20)62 -Fe(HsO)63 ] and by explicit quantum mechanical inclusion of their valence electrons [Fe(HgO)s2 -Fe(H20)s3+] (as defined by the dashed rectangle in Figure 1). The corresponding values of Kei, the electronic transmission factor, are displayed for various Fe-Fe separations of interest.

The Accelerated Convergence Method and the Electrostatic Potential in a Point-Charge Crystal... 

The electrostatic properties of a point-charge crystal are given by the direct space sum... 

The electrostatic potential in a crystal of spherical atoms or ions is therefore the sum of the electrostatic potential of a point-charge crystal and a penetration correction. Only atoms for which the product of RuCj is small contribute to the... 

For the unit-point-charge crystal, the absolute value of the electrostatic energy is equal to the potential at the nuclear position. This potential will be equal for both ions in the alkali halide structure, as their positions are equivalent that is,... 

Fig. 3. Schematic correlation diagram showing excitation energies for Co " in various environments. Left to right free ion ion in point charge crystal field energies from cluster calculation in bulk site energies from cluster calculations in surface site experimental bulk excitation energies. The inset shows schematic one-electron 3d energy levels in bulk and surface sites. Adapted from ref. 91.

Rather little is known about the d—d spectra of bromocuprates(II). Ludi and Feitkneckt (1963) reported the powder reflectance spectrum of CuBr2 and observed a single broad band around 12 kK. Day (1964) gave a point charge crystal field treatment of CuBr2, and Day and Jorgensen... 

Day, P. (1964) Point charge crystal field calculations for cupric halides. Proc. Chem. Soc. (London) 18. 

Fig. 3. Schematic depiction of the octahedral point charge crystal field model. In the free ion, the set of five d orbitals is degenerate. When the ion is placed in a solid and bonds to six nearest neighbor ligands arranged in an octahedral geometry, the d orbitals split into eg (dz, dz2 y0 and t2g (dxy, dxy,dyz) subsets separated by an energy lODq...

Free metal ion Metal ion plus ligands Splitting due to (negative point charges) crystal field... 

Day, G. M., Motherwell, W. D. S., 8c Jones, W. (2005). Beyond the isotropic atom model in crystal structure prediction of rigid molecules Atomic multipoles versus point charges. Crystal Growth and Design, 5,1023-1033. 

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