Tetrahedral structure equation

Similar classification criteria may be made by using the total valence-electron concentration previously defined (see equation 4.27) and defining, according to Parthe (1995) the tetrahedral structure equation ... 

ABSTRACT. For compounds with tetrahedral structure or anionic tetrahedron complex two valence electron concentration rules can be formulated which correlate the number of available valence electrons with particular features of the crystal structure. These two rules are known as the tetrahedral structure equation where the total valence electron concentration, VEC, is used as parameter and the generalized 8 - N rule where the parameter of interest is the partial valence electron concentration in respect to the anion, VEC. From the tetrahedral structure equation one can calculate the average number of non-bonding orbitals per atom and, in the case of non-cyclic molecular tetrahedral structures, the number of atoms In the molecule. An application of the generalized 8 - N rule allows the derivation of the average number of anion -anion bonds per anion or the number of valence electrons which remain with the cation to be used for cation - cation bonds and/or lone electron pairs. These rules have been used not only to predict probable structural features of unknown compounds but also to point out possible errors in composition or structure of known compounds. 

There are known many iono-covalent compounds where only the anions adopt a tetrahedral structure. In a formalistic approach one may assume that the cations transfer all the valence electrons to the anions. The tetrahedral structure equation can then be applied to the charged anion partial structure. We shall use primed parameters, such as VEC, N nbo indicate that we refer to a charged anion partial... 

In analogy to (3) and (11) one can now write the tetrahedral structure equation as applied to the charged tetrahedral anion partial structure (Parth , 1989) as... 

The imxMed tetrahedral structure equation. The tetrahedral structure equation... 

Low-temperature P NMR studies showed that the energy difference between the edge-shared bitetrahedral and bis(edge-capped) tetrahedral structures is very small. The An cluster having pentagonal bipyramidal geometry was synthesized from the gold vapor as shown in equation (15). 

H2O is a major detonation product. A simple exp-6 potential model, however, does not naturally represent the hydrogen-bonded tetrahedral structure of water. We find that an effective two-species model is effective in representing the equation of state of supercritical water over a wide range of conditions. In the two-species model, we represent water by two species in chemical equilibrium non-associated water (H2O) and associated water H20(a). The non-associated water has standard state parameters given by gaseous water. In associated water, however, standard state parameters are chosen closer to that of liquid water the standard enthalpy and entropy are both less than that of gaseous water. 

Both SiF4 and SiCli are molecular with tetrahedral structures. They react readily with water, but the former is only partially hydrolysed (compare equations 14.52 and 14.53). Controlled hydrolysis of SiCLi results in the formation of (Cl3Si)20, through the intermediate SiClsOH. 

The equated lithium ion has a four-coordinate, tetrahedral structure ( ) the model for reaction (85) then becomes ( )... 

Note that the tetrahedreil structure equation describes a necessary but not sufficient condition for the occurrence of a tetrahedral structure. For a discussion of the other conditions, which can not always be formulated In a precise mathematical manner, see Parthe (1990). 

One can write the valence electron equation for tetrahedral structures as follows 4 = 8 - VEC + Nnbo... 

The drawings are complemented with text blocks detailing the numerical values of the different parameters which can be calculated from the valence electron equations discussed above. On top is given the total valence electron concentration, VEC. If VEC < 4 a tetrahedral structure involving all atoms is impossible. The parameters listed below VEC are derived from the valence electron concentration of the charged anion partial structure, VEC, and the next one from the partial valence electron concentration in respect to the anion, VECa- parameter C AC, to be discussed in the next paragraph, refers to the sharing of the anions and can be calculated from the composition of the compound. Finally, on the last row one finds a classification code for the base tetrahedron, also to be discussed later on. 

Some phosphoranyl radicals appear to have approximate tetrahedral structures, for example, 13.190a,b. Another type of phosphoranyl radical is indicated in Equation 13.190c. In this case... 

Only the hydrophobic and steric terms were involved in these equations. There are a few differences between these equations and the corresponding equations for cyclo-dextrin-substituted phenol systems. However, it is not necessarily required that the mechanism for complexation between cyclodextrin and phenyl acetates be the same as that for cyclodextrin-phenol systems. The kinetically determined Kj values are concerned only with productive forms of inclusion complexes. The productive forms may be similar in structure to the tetrahedral intermediates of the reactions. To attain such geometry, the penetration of substituents of phenyl acetates into the cyclodextrin cavity must be shallow, compared with the cases of the corresponding phenol systems, so that the hydrogen bonding between the substituents of phenyl acetates and the C-6 hydroxyl groups of cyclodextrin may be impossible. 

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