Moments population analysis

CHEM3D http //www.camsoft.com/ + + + Transition structures, dipole moments, population analysis, polarizability, ete. 

Molecular descriptors must then be computed. Any numerical value that describes the molecule could be used. Many descriptors are obtained from molecular mechanics or semiempirical calculations. Energies, population analysis, and vibrational frequency analysis with its associated thermodynamic quantities are often obtained this way. Ah initio results can be used reliably, but are often avoided due to the large amount of computation necessary. The largest percentage of descriptors are easily determined values, such as molecular weights, topological indexes, moments of inertia, and so on. Table 30.1 lists some of the descriptors that have been found to be useful in previous studies. These are discussed in more detail in the review articles listed in the bibliography. 

The remainder of the optimization output file displays the population analysis, molecular orbitals (if requested with Pop=Reg) and atomic charges and dipole moment for the optimized structure. 

We ve specified five excited states with NSlotes=5 (the reasons will be clear in a moment). The DensitysAll keyword tells Gaussian to perform the population analysis using all available densities the SCF (ground state) density, the Cl one-partide density, and the Cl (Cl-Singles) density. The population analyses using excited state densities will be performed for the first excited state (the default if the Root option is not included), which is the one in which we are interested. 

The quality of the ) states has been tested through their energy and also their transition moment. Moreover from the natural orbitals and Mulliken populations analysis, we have determined the predominant electronic configuration of each ) state and its Rydberg character. Such an analysis is particularly interesting since it explains the contribution of each ) to the calculation of the static or dynamic polarizability it allows a better understanding in the case of the CO molecule the difficulty of the calculation and the wide range of published values for the parallel component while the computation of the perpendicular component is easier. In effect in the case of CO ... 

However, the behavior of the local descriptors of reachvity is somewhat different. The local quantities are calculated using the Lowdin-based method of population analysis [47], It was observed that when the electric held is applied toward the more electronegative atom of the systems HF and HCN, the value of its nucleophilicity (CFF for electrophilic attack) decreases with increasing held strength (Figure 25.2c). The variation of FF can be well supported with the variation in the induced dipole moment, given in Table 25.1, of the species in... 

The IAM model further assumes the atoms in a crystal to be neutral. This assumption is contradicted by the fact that molecules have dipole and higher electrostatic moments, which can indeed be derived from the X-ray diffraction intensities, as further discussed in chapter 7. The molecular dipole moment results, in part, from the nonspherical distribution of the atomic densities, but a large component is due to charge transfer between atoms of different electronegativity. A population analysis of an extended basis-set SCF wave function of HF, for example, gives a net charge q of +0.4 electron units (e) on the H atom in HF for CH4 the value is +0.12 e (Szabo and Ostlund 1989). 

One interesting species, unknown until recently, is HOF, which was studied by Peslak et al.,611 and electron-density contour maps were described. More recently, it was studied by Kim and Sabin.512 The computed bond lengths with a near-minimal GTO basis were i (H—O) = 1.080 A, J (0—F) = 1.450 A, and 0 = 100.8°, in fair agreement with the results of a microwave investigation. Force constants were computed and the population analysis was reported. A more extensive basis set was used in a similar calculation by Ha, who computed a dipole moment of 2.72 D.513... 

The Mulliken population analysis data (QM and OP), as well as dipole moments, p, for group-6 oxyhalides are given in Table 7. Both the DFT and RECP results show a decrease in QM and an increase in OP from the W to Sg compounds, with the values being very similar. The RECP p are somewhere larger than the DS-DV ones, but both values show an increase in p from the W to Sg oxyhalide. 

Table 7. The Mulliken population analysis data (Qm and OP) and dipole moments (p) for MQ2C12 (M = W and Sg) ...

Thole, B.T. and Duijnen P.Th. van, A general population analysis preserving the dipole moment. Theor. Chim. Acta (1983) 63 209-221. 

The final energy is computed, and a dipole moment and Mulliken population analysis is performed using the final one-electron density matrix. 

Fig. 11 Relative size and orientation of dipole moment vectors of the ground state black) and the excited states JMLCT (bJA ), 3IL (b3A"), and 3MLCT (a3A") of [Re(Etpy)(CO)3(bpy)]+, projected onto the optimized ground-state molecular structure. Dipole moment vectors originate in the center of charge calculated using Mulliken population analysis. They lie in the molecular symmetry plane. (Calculated by TD-DFT G03/PBE0/vacuum at the optimized ground state geometry.) Reproduced with permission from [76]...

Population Analysis Based on the Electrostatic Potential 220 11.7.2 The Dipole Moment of CO 286... 

---