Dipole moment Hartree-Fock

Gaussian also predicts dipole moments and higher multipole moments (through hexadecapole). The dipole moment is the first derivative of the energy with respect to an applied electric field. It is a measure of the asymmetry in the molecular charge distribution, and is given as a vector in three dimensions. For Hartree-Fock calculations, this is equivalent to the expectation value of X, Y, and Z, which are the quantities reported in the output. 

We ran an SCRF single point energy calculation for gauche dichloroethane conformers in cyclohexane (e=2.0), using the Onsager model at the Hartree-Fock and MP2 levels of theory (flfl=3.65) and using the IPCM model at the B3LYP level. The 6-31+G(d) basis set was used for all jobs. We also ran gas phase calculations for both conformations at the same model chemistries, and an IPCM calculation for the trans conformation (SCRF=Dipole calculations are not necessary for the trans conformation since it has no dipole moment). 

With the exception of very large systems, e.g., polymer strands (Chapter 18) and polypeptides and polynucleotides (Chapter 16), all calculations have been carried out using ab initio Hartree-Fock theory with the 3-21G basis seF. The perfomance of this technique with regard to the calculation of geometries, relative energies, dipole moments and vibrational frequencies has been extensively documented. ... 

Force Constants and Dipole-Moment Derivatives of Molecules from Perturbed Hartree-Fock Calculations I J. Gerratt and I. M. Mills Journal of Physical Chemistry 49 (1968) 1719... 

Similar considerations apply to the electric dipole moment the derivatives of the dipole integrals can be easily obtained whilst the derivatives of the density matrix require the use of coupled Hartree-Fock theory (e.g. Gerratt and Mills, 1968). 

As a consequence, field methods, which consist of computing the energy or dipole moment of the system for external electric field of different amplitudes and then evaluating their first, second derivatives with respect to the field amplitude numerically, cannot be applied. Similarly, procedures such as the coupled-perturbed Hartree-Fock (CPHF) or time-dependent Hartree-Fock (TDHF) approaches which determine the first-order response of the density matrix with respect to the perturbation cannot be applied due to the breakdown of periodicity. 

Gatti, C., Silvi, B. and Colonna, F. (1995) Dipole moment ofthe water molecule in the condensed phase a periodic Hartree-Fock estimate, Chem. Phys. Lett., 247, 135- 141. 

Hartree-Fock, DFT or CCSD levels. Because they can reproduce such quantities, APMM procedures should account for an accurate description of the interactions including polarization cooperative effects and charge transfer. They should also enable the reproduction of local electrostatic properties such as dipole moments an also facilitate hybrid Quantum Mechanical/Molecular Mechanical (QM/MM) embeddings. 

Poly(aminoborane) has a relatively simple structure, as shown in Figure 9. Jacquemin and co-workers [63] performed a comprehensive set of calculations to investigate the infrared spectra, vertical excitation energies, geometries, atomic charges and dipole moments as a function of conformation. A variety of theoretical methods were employed, including Hartree-Fock, MP2 and... 

In this next section the dipole magnitude and directionality from MM3(2000) is compared to results obtained by MM3(96), Hartree-Fock and Mdller-Plesset minimized structures (calculated using GAUSSIAN94),77 as well as experimental dipole moment measurements.78 For the molecular mechanics geometry optimizations, full matrix energy minimizations were carried out, and ground state structures were verified by the vibrational... 

The differences between ab initio and molecular mechanics generated dipole moments were discussed. The MM3(2000) force field is better able to reproduce experimental dipole moments for a set of forty-four molecules with a root mean squared deviation (rmsd) of 0.145 Debye compared with Hartree-Fock (rmsd 0.236 Debye), M0ller-Plesset 2 (rmsd 0.263 Debye) or MM3(96) force field (rmsd 0.164 Debye). The orientation of the dipole moment shows that all methods give comparable angle measurements with only small differences for the most part. This consistency within methods is important information and encouraging since the direction of the dipole moment cannot be measured experimentally. 

This chapter assesses the performance of quantum chemical models with regard to the calculation of the magnitudes of dipole moments. (Too little experimental information is available about the sign and/ or direction of dipole moments or about higher moments to make comparisons of these quantities with the results of calculations of value.) Coverage is divided according to type of molecule diatomics and small polyatomics, hydrocarbons, molecules with heteroatoms and hypervalent molecules. Models examined include Hartree-Fock... 

As seen from comparison of data in Tables AlO-l and AlO-2, local density models parallel the behavior of the corresponding Hartree-Fock models. Except for highly polar ( ionic ) lithium and sodium compounds, dipole moments are generally larger than experimental values. Recall that local density models typically (but not always) exhibit the same systematic errors in bond lengths (too short) and stretching frequencies (too large) as Hartree-Fock models. 

Hartree-Fock, local density, density functional and MP2 models provide a credible account of dipole moments in hydrocarbons. Even STO-3G and 3-2IG (Hartree-Fock) models appear to be suitable. Not only is the mean absolute error very low (0.1 debye or less), but all models properly account for a variety of subtle trends in the experimental data, for example, the increase in dipole moment in cyclopropene in response to methyl substitution on the double bond. Finally, note that there is very little difference in the performance of any of the models with 6-3IG and 6-311+G basis sets. 

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