Bond angle distributions

Fig. 5.7. Simplified schematic flow chart for the optimization of the parameters of the bond length and bond angle potentials. The input parameters from the chemically realistic model are the moments (L), (L2), ( ), (02), (LG) taken from the bond length and bond angle distributions, and the reduced effective barrier (W) from the torsion potentials. From Tries [184]... 

From the covariance map, in which the covariance coefficients [17] are plotted on a two-dimensional plane, we can identify the respective explosion pathways and show how the momentum components along the TOF axis of the different ion species are correlated. The characteristic patterns appearing in the double covariance map for the ion pairs (0+, 0+), (0+, C+) and (0+, 02+) ejected from C02 at the field intensity of 1015 W/cm2 were interpreted in terms of a large amplitude bending motion [18], where the widths of the bond angle distribution were found to be constant different charge states (z = 3-6). 

Among the bond angle distributions, the most spectacular change is that shown by A3 (Figure 17c) revealing a trimodal character. The frequency maxima at about 95 °, 110° and 122° can be ascribed to the presence of the N1 atom in a four-membered... 

The bond length and bond angle distributions for the OwH O, and C-OH -Ow bonds are shown in Fig. 22.1. The two-center bonds and the major components of the three-center bonds have a relatively narrow distribution with most probable H 0 bond lengths of 1.75 A and 1.87 A respectively. The minor components of the three-center bonds extend from 1.9 to 2.25 A. 

Fig. 8.4. The Si-O-Si bond angle distribution in undensified (solid line) and den-sified (dashed line) amorphous SiOj ( suprasil I ) derived from NMR line shapes, where (6) is the relative number of bridging oxygens with bond angle 0 (after Devine et al., 1987 reproduced with the publisher s permission).

Dupree, E., and R. F. Pettifer (1984). Determination of the Si-O-Si bond angle distribution in vitreous silica by magic angle spinning NMR. Nature 308, 523-25. 

The distributions of the U-Obr-T bond angles for different T elements are shown in Fig. 74. It is of interest that the bond angle distributions for 7= S, Cr and Se are much more sharp than one for T= Mo. 

One of the most powerful applications of these correlations between NMR parameters and stmcture is to provide a better understanding of the stmcture of amorphous materials which are very difficult to study by other techniques. Silicate glasses have been studied by relating the 8iso.cs value of Si to the bond angle distribution (Dupree and Pettifer 1984, Pettifer et al. 1988). In the case of O, the parameter has been used to determine the Si-O-Si bond angle distribution (Faman et al. 1992) using the relationship ... 

Although the origin of low temperature anomaly is unclear, the low pressure anomaly has been attributed to the presence of two different populations of Si-O-Si bond angles. The Si-O-Si bond angle distribution is... 

Bond Length and Bond Angle Distribution Functions... 

Figure 20. Nearest-neighbor bond angle distribution functions for the time-averaged 3584-particle WCA liquid at p = 0.83. The figure shows the contributions from ordered regions (dotted line), disordered regions (dashed line), and the overall distribution (solid line). The horizontal scale is in degrees.

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