Mulliken charge effect

Fig. 2.7 Comparison of the Mulliken charges computed for 4-pyridone using the AMI semi-empirical model in (a) the gas-phase, and (b) water (bold) using the SM2 solvation model. The effect of including solvent is to increase the magnitude of the molecular dipole.

Figure 2 Magnetic shielding constants a (ppm) on H (a) and C (b) cage atoms and their Mulliken s effective charges (c) in MO C60H36(r) clusters.

Turning to the expression of orbitals and solvent effect on CN and CC1 bond polarization. Because of the simplicity of Equations (24) and (25), it is convenient to perform a Mulliken population analysis (see for example [26]) on the above orbitals at different CC1 distances in vacuo and in solution. In terms of contributions coming only from and (f>z, the Mulliken charges on nitrogen and chlorine turn out to be as follows... 

Fig. 7 shows the behaviour of these charges with variation of the CC1 distance. As was to be expected in going towards the products, namely CH3NH3 and Cl-, Qn tends to a minimal value while qci tends to unity. The effect of water, the solvent, results in a further enhancement of qci and in a further reduction of qjy with the increase of CC1 distance. This effect is completely due to the solvent polarization when the ionic products begin to form. It is important to note that such small changes in the Mulliken charges (27) and (28) correspond instead to a strong change in the value of the energy along the reaction path (see Fig. 6). Repulsion and dispersion contributions to the solvation free energy do not have any visible effects on the solute wavefunction in this reaction.

Thirdly, we examined the ion-implantation effect on the bond between composite atoms of 813X4. When Fe, Mo and Hf atoms are supposed to be ion-implanted, d energy levels of these atoms appear in the energy gap or near the gap. A transfer of the Mulliken charge between the implanted atoms and surrounding atoms occurs due to the mixing between the d orbitals of the... 

The theory behind these was given in section 5.5.4. Recall that these parameters are not observables and so there are no experimental, right values to aim for electrostatic potential charges and Lowdin bond orders are preferred to Mulliken charges and bond orders. The effect of various computational levels on atom charges has been examined [80]. 

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