A method to derive the atomic multipole moments cumulatively up to quadrupole mo- ments was developed.The multipole moments are obtained by least-square simulating the molecular electrostatic potentials.Only the compo...A method to derive the atomic multipole moments cumulatively up to quadrupole mo- ments was developed.The multipole moments are obtained by least-square simulating the molecular electrostatic potentials.Only the components of the term of highest order in the atomic multipole expansion are optimized while the lower terms remain fixed.The calculations on HF,H_2O and NH_2 show that the cumulative method can give reasonable qualitative and fairly good quantitative results.展开更多
The suitability of calculating atomic multipole moments from AM1 wave functions by cumulative potential-derived method has been investigated. It is shown that this method has a faster convergence of the fitting proces...The suitability of calculating atomic multipole moments from AM1 wave functions by cumulative potential-derived method has been investigated. It is shown that this method has a faster convergence of the fitting process and gives a better description of the charge distribution than the original PD method. Atomic charges obtained in this way are of comparable quality with 6-31G* data and the calculated dipole moments are closer to the experimental data than the values computed directly from the AM1 charges. The results demonstrate that the atomic multipole moments higher than monopole moment can be used to supplement the atomic charge to obtain a more accurate description of charge distribution. For the sake of comparison, both the Williams fitting potential surface and the Connolly one are used in the calculation.展开更多
基金This work was supported by the National Natural Science Foundation of China.
文摘A method to derive the atomic multipole moments cumulatively up to quadrupole mo- ments was developed.The multipole moments are obtained by least-square simulating the molecular electrostatic potentials.Only the components of the term of highest order in the atomic multipole expansion are optimized while the lower terms remain fixed.The calculations on HF,H_2O and NH_2 show that the cumulative method can give reasonable qualitative and fairly good quantitative results.
文摘The suitability of calculating atomic multipole moments from AM1 wave functions by cumulative potential-derived method has been investigated. It is shown that this method has a faster convergence of the fitting process and gives a better description of the charge distribution than the original PD method. Atomic charges obtained in this way are of comparable quality with 6-31G* data and the calculated dipole moments are closer to the experimental data than the values computed directly from the AM1 charges. The results demonstrate that the atomic multipole moments higher than monopole moment can be used to supplement the atomic charge to obtain a more accurate description of charge distribution. For the sake of comparison, both the Williams fitting potential surface and the Connolly one are used in the calculation.
