Bond length/order

Atomic Charges, Bond Lengths, Orders, and Energies of the N-Halogen Bond for Some 1-X-l,2,4-triazoles [98ZOR(ip)J... 

Figure 3 Structure of the MeSiy thiometallates. The bond length order is M-S terminal < M-/uS

The optical absorbance of pernigraniline base. Fig. 8, though similar to that of EB is different in origin. In particular, the 2.3 eV absorption in PNB has been assigned to the excitation across a Peierls energy gap. This Peierls gap has been proposed to arise from two independent contributions, variation in bond length order parameter and variation in ring torsion... 

Compared with the Morse potential, Hooke s law performs reasonably well in the equilibrium area near If, where the shape of the Morse function is more or less quadratic (see Figure 7-9 in the minimum-energy region). To improve the performance of the harmonic potential for non-equilibrium bond lengths also, higher-order terms can be added to the potential according to Eq. (21). 

In order to consider the 3D structure but make the chirality code independent of a specific conformer, r- is taken as the sum of the bond lengths between atoms i and j on the path with a minimum number of bond counts. 

There are several variations of this method. The PRDDO/M method is parameterized to reproduce electrostatic potentials. The PRDDO/M/FCP method uses frozen core potentials. PRDDO/M/NQ uses an approximation called not quite orthogonal orbitals in order to give efficient calculations on very large molecules. The results of these methods are fairly good overall, although bond lengths involving alkali metals tend to be somewhat in error. 

Finally, the CN and CC 7r-bond orders can be determined by use of a relation between bond orders and bond length (122) and the experimentally measured bond length (159). 

TABLE 1-9. 7T-BOND ORDERS AND BOND LENGTHS IN ALL-VALENCE-ELECTRONS CALCLn..A-TIONS... 

Bond orders calculated from experimental bond lengths (122i. 

In Table 1-9 we have collected only the 7r-bond orders calculated by allvalence-electrons methods and compared their values with those deduced from experimental bond lengths. Both data are indicative of an aromatic molecule with a large dienic character. The 2-3 and 4-5 bonds especially present a large double-bond character, whereas both C-S bonds are relatively simple. 

Molecular Dynamics and Monte Carlo Simulations. At the heart of the method of molecular dynamics is a simulation model consisting of potential energy functions, or force fields. Molecular dynamics calculations represent a deterministic method, ie, one based on the assumption that atoms move according to laws of Newtonian mechanics. Molecular dynamics simulations can be performed for short time-periods, eg, 50—100 picoseconds, to examine localized very high frequency motions, such as bond length distortions, or, over much longer periods of time, eg, 500—2000 ps, in order to derive equiUbrium properties. It is worthwhile to summarize what properties researchers can expect to evaluate by performing molecular simulations ... 

Bond lengths and infrared spectra support the multiple-bond character of the M—CO bonds. Coordination of a CO molecule to a metal center can change the C—O bond order. According to the description of ( - and TT-bonding given herein, increased ( -bonding between a metal and CO results in a... 

The indazole molecular structure (Figure 11) shows the tautomeric proton bonded to N-1 (1//-indazole. Section 4.04.1.5.1). A linear correlation between the bond lengths and the bond orders calculated by the CNDO/2 method was observed (74T2903). 

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