Ab initio calculations of dipole moments

Cheam, T. C., and S. Krimm. 1985. Infrared Intensities of Amide Modes in N-methyl-acetamide and Poly(Glycine I) From Ab Initio Calculations of Dipole Moment Derivatives of N-methylacetamide. J. Chem. Phys. 82, 1631-1641. 

Semiempirical optimization of molecular structures and ab initio calculations of dipole moments of nitrobenzoxazole family of potential nonlinear optic materials have been carried out [1202], Clear evidence was found that conditions such as conjugation efficiency and electron donor/acceptor strength cannot be evaluated separately, due to structural changes in molecular distribution. 

The number of papers with ab initio calculations of dipole moments of heterocycles has been continually increasing throughout the last few years. Today, ab initio dipole moments are available for most major parent heterocyclic systems and numerous derivatives, especially the nitrogen-containing heterocycles in general and pyrimidine and purine bases in particular. A number of different basis sets and approaches were used. 

As underlined above, the ab initio calculations of dipole moment derivatives are strongly interrelated widi the respective force field calculations. In fact, as shown by Komomicid and Mclver [178], die dipole derivatives can be derived efficiently fi om the energy gradients dE/dq, where q are coordinates describing nuclear motions. 

Here the summation of charges times position vectors is replaced by the integral over the total waveftmction I (the square ofthe wavefunction is a measure of charge) ofthe dipole moment operator (the summation over all electrons ofthe product of an electronic charge and the position vectors of the electrons). To perform an ab initio calculation ofthe dipole moment of a molecule we want an expression for the moment in terms of the basis functions , their coefficients c, and the geometry (for a molecule of specified charge and multiplicity these are the only variables in an ab initio calculation). The HF... 

W. Meyer. Ab initio calculations of collision-induced dipole moments. In G. Birnbaum, ed., Phenomena Induced by Intermolec. Interactions, p. 29, Plenum Press, New York, 1985. 

W. Meyer and L. Frommhold. Ab initio calculations of the dipole moment of He-Ar and the collision induced absorption spectra Phys. Rev., A 33 3807, 1986. 

De Boer and coworkers ° °" parameterized the shell model for silica polymorphs on the results of ab initio calculations of the potential energy surfaces, polarizabilities, and dipole moments of Si(OH)4 and (0H)3Si-0(H)-Si(OH)3 clusters. The structural characteristics and elastic moduli calculated with this set of parameters for three structures compared well with results computed with the use of both the rigid ion and the empirical shell models. ... 

Once internal modes are defined, it is also possible to define the infrared intensity of these modes. For a normal mode, the infrared intensity is calculated with the help of the dipole moment derivatives. The dipole derivatives 3p/5x with regard to Cartesian coordinates can be determined in the course of an ab initio calculation of vibrational frequencies. The corresponding dipole derivatives with regard to normal coordinates are obtained by the transformation... 

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