Ion distortion

Fig. 12.2 Ion distortion by the field in the vicinity of a negative cathode, (a) Diffusion of anion to cathode, (b) diffusion and migration of distorted complex and (c) release of CN ions and incorporation of Ag into the lattice...

Figure 5.10 Representation of the formation of the lone pair in the PF3 molecule, (a) An isolated P3 + ion consisting of a P5+ core surrounded by two nonbonding electrons in a spherical distribution, (b) Three approaching F ions distort the distribution of the two valence shell electrons pushing them to one side of the P5+ core, (c) When the F ligands reach their equilibrium positions, the two nonbonding electrons are localized into a lone pair, which acts as a pseudo-ligand giving the PF3 molecule its pyramidal geometry.

The qualitative elements of Marcus theory are readily demonstrated. For example, the process of transferring an electron between two metal ions, Fe2+ and Fe3 +, may be described schematically by Fig. 33 (Eberson, 1982 Albery and Kreevoy, 1978). The reaction may be separated into three discrete stages. In the first stage the solvation shell of both ions distorts so that the energy of the reacting species before electron transfer will be identical to that after electron transfer. For the self-exchange process this of course means that the solvation shell about Fe2+ and Fe3+ in the transition state must be the same if electron transfer is not to affect the energy of the system. In the second phase, at the transition state, the electron is transferred without... 

The possible explanation [233] for the environmental sensitivity of the transitions (nonhypersensitive) may be due to an increase in 7) parameters which results in lowering of the excited states of the ions since the surrounding crystal field is influenced by the symmetric part of the crystal field. The observed changes in 7 and the small nephelauxetic effect show that the nonsymmetric part of the crystal field affects 7 values. The modifier ions distort the oxygen bonded to the lanthanide and thus lowers the site symmetry and increases the f-f transition probability. 

AFm phases have layer structures derived from that of CH by the ordered replacement of one Ca ion in three by AF" or Fe (Fig. 6.1) (A7-A9). The principal layers thus defined alternate with interlayers containing the X anions, which balance the charge, and H2O molecules. The replacement of Ca by the smaller AF or Fe " ions distorts the structure of the principal layer, alternate Ca ions moving in opposite directions from its central plane. This allows each to coordinate the oxygen atom of an interlayer HjO molecule in addition to its six OFI ions. The principal layer, together with the H2O molecules thus bonded to the Ca ions, has the composition [Ca2(Al,Fe)(0Fl)g-2Fl20]. In the simpler AFm structures, these units are stacked in such a way as to produce octahedral cavities surrounded by three FljO molecules from each of the adjacent layers. These cavities may contain... 

SF5- has a single lone pair. Its structure is based on an octahedron, with the ion distorted away from the lone pair, as in IF5. 

The effect of individual reactants on the tetrahedral and cubic platinum nanoparticles was investigated in order to determine which reactants were responsible for the distortion of the nanoparticles [40]. There was significant dissolution of atoms from the comers and edges of both the tetrahedral and cubic platinum nanoparticles upon exposure to hexacyanoferrate (III) ions. Distorted tetrahedral and cubic platinum nanoparticles became the dominant shape (Fig. 18.3b and d, respectively). The distortion in shape of the nanoparticles was proposed to be due to the cyanide ligand of the hexacyanoferrate (III) ions adsorbing and reacting with the platinum comer and edge atoms of the nanoparticles to form Pt(CN) " complexes. 

Under pressure Rb4C6o undergoes a phase transition to an orthorhombic phase similar to that of CS4C60 [63]. Previously it was believed that Rb4C6o transforms into a metallic phase under pressure [64]. In a recent thorough study, though, no such transition has been found up to 2 GPa [65]. The nature of the fulleride ion distortion in the orthorhombic Rb4C6o is as yet unknown. 

Although degenerate orbitals in an isolated ion are partially lifted in a molecule and in a solid, the degeneracy often partially remains in a crystal lattice with high symmetry. In a molecule, this degeneracy is lifted by ion distortions, i.e. the Jahn-Teller distortion. However, in a crystal lattice, an infinite number of degrees of... 

Internuclear distance. See Bond length Inert gas solids Simple metals Transition metals Intra-atomic Coulomb energy, 431, 527ff Intrinsic semiconductors, 152 Ion, 33, 289-338 Ion distortion, 190f Ion polarizability, 326f... 

The principal component present in CAC is calcium monoaluminate (CA in cement chemistry nomenclature, see Table 2.3). Its structure resembles that of P-tridymite, one of the polymorphs of Si02. Rather than having [SiOJ" " tetrahedral sharing corners in CA we have [AlOJ tetra-hedra. The large Ca ion distorts the tridymite network and the structure is monoclinic. 

Robinson, E.W., Shvartsburg, A.A., Tang, K., Smith, R.D., Control of ion distortion in field asymmetric waveform ion mobility spectrometry via variation of dispersion field and gas temperature. Anal. Chem. 2008, 80, 7508. 

Between 9.7 and 10 K, the Mdssbauer spectram of the Cr2FeS4 shows an abrapt change in the electric field gradient, which indicates a low-temperature transition [1972Spe]. It is possible that a-sites, which are occupied by Fe ions, distort tetragonally with da < 1 below 10 K. 

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