Comparison of atomic charge distributions obtained from different procedures: basis set and electron correlation effects

The atomic charge distributions of dimethyl ether, ethyl methyl ether, methyl alcohol and ethyl alcohol are obtained by Mulliken and natural population analyses and by electrostatic potential (ESP) fitting methods from HF and MP2 wavefunctions with several basis sets up to the 6-311G (2d,2p) basis set. To evaluate the atomic charge distributions, the dipole moments are calculated from the atomic charge distributions. The dipole moments from the atomic charge distributions, which are obtained by the fitting of the electrostatic potentials, are close to those directly obtained from the wavefunctions. They are also close to the experimental dipole moments, if the wavefunctions are calculated with a polarized basis set and electron correlation correction. The dipole moments obtained by the Mulliken and natural population charges are strongly basis set dependent and do not agree with the experimental dipole moments. The same tendency is observed from the calculations of other ethers and alcohols.