Lattice, coordination crystal

Host lattice Coordination Eu2+ ion Absorption bands Crystal field splitting Centre 54 level Ref. 

As a result of the repulsion, the distance between the atoms in a single molecule AB will be larger than it is in the lattice. If the crystal belongs to the NaGl type, then for n we have to take a value of 10 the second term, 12/25 = 0-4, is small compared with the first. As a first approximation, B can be replaced by bcjrn where c is the lattice coordination number. 

These comparatively lipophilic ligands have been conceived as ion carriers for systems such as ion-selective electrodes, 29 therefore they do not have high stability constant values, but require fast complexation kinetics in order to achieve rapid equilibration. Nevertheless, it has been possible to recover crystalline species which often have present additional water molecules to help stabilize the crystal lattice. Coordinative participation of the carbonyl oxygen... 

The correct structure is predicted for BeO, MgO, and CaO, but for SrO and BaO the predicted coordination number is eight, although the structures found are six coordinate. Crystals adopt the structure that has the most favorable lattice energy, and the failure of the radius ratio concept in this case leads us to examine the assumptions on which it is based. Ionic radii are not known with great accuracy and they change with different coordination numbers (Table 7). Also, ions are not necessarily spherical, or inelastic (see Structure Property Maps for Inorganic Solids) ... 

Compound 1 shows many intermolecular interactions. Firstly, the packing plot (but also the 3-D atom coordinate list) reveals that no solvent molecules are included in the crystal lattice. The crystallization was done from ethanol, but ethanol molecules are not included into the crystal lattice. The packing plot (Fig. 9.14) shows that an intermolecular interaction between the moledues, i.e. re-re stacking, creates an antiparallel pair of 1 with short non-bonded contact distance of 3.30 A... 

The reciprocal lattice coordinates, , , T, v, etc, used earlier refer to an axial system which rotates with the crystal, i.e. Xo, Yo, Zo of figure A 1.3. Clearly, a given RLP needs to be brought onto the Ewald sphere by the rotation about the rotation axis. We now follow the treatment of Arndt and Wonacott (1977). 

The value of crystal rocking width for a given hkl, depends on the reciprocal lattice coordinates of the hkl RLP (see chapter 6). In the region close to the rotation axis 0R is large. Any reflection with 0R> A0max is defined to lie in the blind region. 

The generation of hydrous films on platinum at low potentials on the anodic sweep seems quite feasible from a thermodynamic viewpoint—especially in base. The inhibition here is evidently related to the need for six hydroxide ions to have access to coordination sites at the same platinum atom—an improbable condition for a metal atom in a regular surface site. Evidence will be presented later indicating that such hydrous oxide formation can, to a very limited extent, precede monolayer formation in the case of gold— the atoms of the latter involved in formation of the hydrous material are presumably at low lattice coordination sites on the surface. There is some evidence from recent single-crystal studies (see Section XIV) for this type of behavior in the case of platinum—it is obviously difficult to detect with polycrystalline substrates as with only a small fraction of a monolayer involved optical techniques would need to be extremely sensitive and electrochemical procedures are hampered by the fact that the redox behavior of the hydrous material coincides with that for adsorbed hydrogen. 

The crystal lattice coordinates, a, b, c, a, p, and y were taken as the variables for energy minimization, and in the case of acetic acid, the packing was studied by changing the methyl hydrogen coordinates as a function of methyl rotation. 

FIGURE 13.1 Repeating the unit cell stracture along the a, b, and c lattice coordinates generates an entire crystal. 

Using the observed lattice energies tabulated below, estimate the magnitude of Aq in octahedrally coordinated crystals of VO, MnO, and FeO. Carefidly explsdn your... 

The empirical pseiidopotential method can be illustrated by considering a specific semiconductor such as silicon. The crystal structure of Si is diamond. The structure is shown in figure Al.3.4. The lattice vectors and basis for a primitive cell have been defined in the section on crystal structures (ATS.4.1). In Cartesian coordinates, one can write G for the diamond structure as... 

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