Oxygen atoms, distance between

Relative concentration of a nucleus at an adsorption site j Average charge on the framework oxygen atoms Distance between two atoms... 

Figure 8 clearly shows that an increase in the electrostatic energy associated with an increase in the tetrahedral cation-basal oxygen atom distance is compensated by a reduction in the repulsion between the interlayer cation and the tetrahedral cation and the tetrahedral-tetrahedral cations (sited in adjacent layers). Given the high correlation coefficient (r = 0.997), the relation may be useful as a predictive tool. 

If the interatomic distance of neighboring oxygen atoms is between 2.4 and 2.8 A, the groups are hydrogen bonded, if this distance exceeds 3.1 A, hydrogen... 

Fig. 15. The bonding scheme of (a) H2O and (b) D2O in crystal. In protonated water, on-centering is preferred, whereas off-centering occurs in deuterated water. The atomic distance between oxygens, doo, varies depending on the interaction.

Fig. 10. Pharmacophores for angiotension-converting enzyme. Distances in nm. (a) The stmcture of a semirigid inhibitor and distances between essential atoms from which one pharmacophore was derived (79). (b) In another pharmacophore, atom 1 is a potential zinc ligand (sulfhydryl or carboxylate oxygen), atom 2 is a neutral hydrogen bond acceptor, atom 3 is an anion (deprotonated sulfur or charged oxygen), atom 4 indicates the direction of a hydrogen bond to atom two, and atom 5 is the central atom of a carboxylate, sulfate, or phosphate of which atom 3 is an oxygen, or atom 5 is an unsaturated carbon when atom 3 is a deprotonated sulfur. The angle 1- -2- -3- -4 is —135 to —180° or 135 to 180°, and 1- -2- -3- -5 is —90 to 90°.

The alkaloid Nigellicine proved to be the pyridazino[l,2-u]indazolium-l 1-carboxylate (234) and forms yellow crystals (Scheme 77). It was isolated from the widely distributed herbaceous plant Nigella saliva L., which is used as a spice and for the treatment of various diseases (85TL2759). The structure was determined by an X-ray crystal structure analysis. The carboxylate bond distances are essentially equal (123.3 and 125.6 pm). An intramolecular hydrogen bond was found between the carboxylate oxygen atom and the hydroxy group. In mass spectrometry, the molecular peak was found at mjz —246 (20) and the base peak at mjz —202 which corresponds... 

Finally, the use of the constant pressure minimization algorithm allows searching for phenomena that can be considered as precursors of pressure-induced transitions. For example, the predicted behaviour of the anatase cell constants as a function of pressure shows that the a(P) and c(P) plots are only linear for P<4 GPa, the value that is close to both the theoretical and experimental transition pressures. At higher pressures the a constant starts to grow under compression, indicating inherent structural instability. In the case of ratile there is a different precursor effect, nami y at 11 GPa the distances between the titanium atom and the two different oxygens, axial and equatorial, become equal. Once again, the pressure corresponds closely to the phase transition point. 

The niobium atom has a slightly distorted octahedral coordination. Interatomic distances between the niobium atom and the two oxygen atoms in trans positions, O-Nb-O are 1.81 and 2.14 A. The niobium atom is shifted from the base plane of the octahedron by 0.23 A, and this shift, in adjacent chains, is in opposite directions. Pakhomov and Kaidalova [204] concluded that the shorter Nb-O bond (1.81 A) is an intermediate between a single and double bond. 

The smaller cavities are distorted pentagon dodecahedra (distance of oxygen atoms to center varies between 3.77 and 3.95 A) their average free diameter is only about 5.0 A. The larger cavities are almost spherical the oxygen atoms lie at the vertices of hexadeca-hedra and their free diameter is 6.7 A. The distances have been calculated on the basis of a unit cell edge of 17.40 A as found for propane hydrate. 

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