Calculation of dipole moment functions with density functional theory: application to vibrational band intensities

We have calculated fundamental and overtone XH stretching vibrational band intensities for H₂O, benzene, cyclohexane, 1,3-butadiene, and HCN. The band intensities were calculated with a simple harmonically coupled anharmonic oscillator local mode model and a series expanded dipole moment function. The dipole moment functions were obtained from local, non-local and hybrid density functional theory calculations with basis sets ranging from 6–31G(d) to 6–311++G(3df,3pd). The calculated band intensities have been compared with intensities calculated with conventional ab initio methods and with experimental results. Compared with conventional correlated ab initio methods, a carefully chosen density functional method and basis set seems to give better fundamental and overtone intensities with far less resources used. We have found that the density functional methods appear to be less sensitive to the choice of basis set, with little difference between the results obtained with a non-local or hybrid density functional method.     

Three-dimensional ab initio dipole moment surfaces and stretching vibrational band intensities of the XH3 molecules

Stretching vibrational band intensities of XH₃ (X=N, Sb) molecules are investigated employing three-dimensional dipole moment surfaces combined with the local mode Hamiltonian model.The dipole moment surfaces of NH₃ and SbH₃ are calculated with the density functional theory and at the correlated MP2 level,respectively. The calculated band intensities are in good agreement with the available experimental data. The contribution to the band intensities from the different terms in the polynomial expansion of the dipole moments of four group V hydrides (NH₃, PH₃,AsH₃ and SbH₃) are discussed. It is concluded that the breakdown of the bond dipole approximation must be considered. The intensity “borrowing” effect due to the wave function mixing among the stretching vibrational states is found to be less significant for the molecules that reach the local mode limit.     

Analysis of band intensities in vibrational spectra of esters and deuteroesters

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 4, pp. 570–574, April, 1991.     

Stopping a vibrational wave packet with laser-induced dipole forces

Intense near-infrared laser pulses can generate laser-induced dipole forces that are strong enough to influence or control vibrational motion of a small molecule. Generally, the force acts to pull the molecule apart. Our numerical simulations show that, by applying the laser-induced dipole force at an appropriate time within one vibrational period, the wave packet motion of H+2 or D+2 can be accelerated or decelerated. Using the wave packet formed by the rapid ionization of H2 or D2, we also show that it is possible to move the vibrational population almost entirely to the v=0 state. Coherent cooling of the molecular vibrational motion can be achieved.     

Calculation of band intensities in vibrational spectra and conformation of chloromethylformate and chloromethylacetate

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 49, No. 1, pp. 70–74, July, 1988.     

Infrared band intensities for isotopic water molecules

Integrated intensities for the three fundamental i.r. bands of HOD, DOD, HOT and TOT are estimated theoretically using Crawford's method. Experimental values have only been reported for HOD; agreement is found to ±8%.     

HCl vibrational fundamental band: Line intensities and temperature dependence of self-broadening coefficients

Self-broadening in the vibrational fundamental of HCl is inversely proportional to the temperature for transitions which lie near the Boltzmann rotational maximum and becomes monotonically less temperature-dependent as the rotational quantum number increases. We have determined the rotationless transition moment to have the value of 5.57 ± 0.13 × 10^?3 (Debye)² and the first Herman-Wallis factor, C = ?2.543 ± 0.019 × 10^?2.     

The dipole moment derivatives and charge flux parameters from vibrational absorption intensities of ethylene oxide

The signs of dipole moment derivatives for ethylene oxide obtained from ab initio calculations using the 6-31G¹ basis set are presented. From these signs and the experimental vibrational absorption intensity data, the atomic polar tensor elements and bond charge flux parameters were evaluated. These quantities were compared with those in the literature calculations employing approximate signs and force constants.     

Ordering of molecular dipole moments in a nanosized water cluster

A water cluster of 1000 molecules is simulated using the method of classical molecular dynamics. The calculation is performed for the “flexible” version of the TIP4P interaction potential for a constant cluster temperature of 180 K. It is found that clusters with a solid crystalline or amorphous core and a liquid-like shell are stable structures. The ferroelectric ordering of the molecular dipole moments in the central part of the cluster is found for both cluster types; this ordering is responsible for a large total dipole moment of these molecular groups. However, this effect is compensated by dipoles in the peripheral cluster layers, so that in general, the mean dipole moment of a cluster appears to be much smaller than that in the case of the random orientation of the cluster molecules.     

CP-violation and electric dipole moments

Searches for intrinsic electric dipole moments of nucleons, atoms and molecules are precision flavour-diagonal probes of new -odd physics. We review and summarise the effective field theory analysis of the observable EDMs in terms of a general set of CP-odd operators at 1 GeV, and the ensuing model-independent constraints on new physics. We also discuss the implications for supersymmetric models, in light of the mass limits emerging from the LHC.     

Electric dipole moments of water clusters from a beam deflection measurement

The response of (H2O)(n=3-18) clusters to an electric field is studied by beam deflection. All clusters deflect uniformly, behaving as polarizable particles. The effective polarizabilities exceed the electronic component and increase as the clusters are cooled, revealing a large permanent dipole contribution. The results resolve a discrepancy concerning the polarity of water clusters and show that all species access conformations with moments exceeding 1 D. The data show no evidence for a freezing transition down to approximately 120 K, but suggest a shift in the conformer arrangement at n=8-9.     

Anharmonic properties of the double giant dipole resonance

A systematic microscopic study of the anharmonic properties of the double giant dipole resonance (DGDR) has been carried out, for the first time, for nuclei with mass number A spanning the whole mass table. It is concluded that the corrections of the energy centroid of the Jpi = 0(+) and 2(+) components of the DGDR from its harmonic limit are negative, have a value of the order of a few hundred keV, and follow an A-1 dependence.     

High order vibrational matrix elements for diatomic molecules; dipole moment function and transition moments of CO

The fifth and sixth-order contributions to the vibrational matrix elements are obtained for the transitions v→v'(v'?v+4) using an eight power internuclear Dunham potential and a quartic power series expansion of the dipole moment function. The results for the dipole moment coefficients M₀ to M₄ of CO and the transition moments R_v^v' (with v=5, 10, 20) deduced from a calculation including succesively third, fourth, fifth and sixth-order perturbation theory are compared. The validity of these results is discussed.Using a quintic dipole moment function, general expressions for the vibrational matrix elements corresponding to the transitions v→v'(v'? v+5) are also presented and the influence of these contributions on the calculation of the dipole moment coefficients as well as the hot band transition moments of CO is shown.     

Absolute infrared intensities in some metal carbonyls and the charge flux model of the dipole derivatives

The absolute intensities of the four infrared active modes of certain metal carbonyls, M(CO)₄ or M(CO)₆, are analyzed from the point of view of the equilibrium charge-charge flux model of the dipole derivatives. It is shown that the charges obtained from the bending modes, assuming negligible flux for these modes, are apparently identical with those reported by previous authors. However, such charges are much too sensitive to the choice of L matrix (which transforms the normal coordinates to symmetry coordinates) to permit any conclusions. The carbonyl stretching mode implies values of the dipole derivative three- to sixfold greater than in gaseous CO. It seems most reasonable to attribute most of this enhancement to charge flux between the metal and carbon atoms.     

Electric dipole moments of nuclei

Recent calculations by Sushkov, Flambaum and Khriplovich have suggested that the existence of the possibility of kaon exchange within nuclei allows nuclear electric dipole moments within the standard model to be enhanced substantially over those of nucleons. This suggestion is analysed carefully and it is found that the constraints of chiral symmetry, which were not correctly included in the earlier calculation, reduce this prediction substantially.     

Anharmonic resonances in the vibrational spectra of pyrazine

The quartic force field of pyrazine has been calculated in the B3LYP/6-31G(d) hybrid density-functional approximation. Based on the results of this calculation, the total IR (250–3800 cm^–1) and Raman (400–3200 cm^–1) spectra of pyrazine have been interpreted with consideration for the Fermi and Darling-Dennison resonances and their spectral manifestations. A precision method is proposed for anharmonic analysis of the vibrational states of polyatomic molecules on the basis of consideration of their theoretical anharmonicity constants in combination with the corresponding experimental frequencies. The method of linear scaling of frequencies has been theoretically substantiated.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 13–22, January–February, 2005.     

Permanent dipole moments and multi-photon resonances

The effects of non-zero diagonal dipole matrix elements on multi-photon resonance profiles, for the interaction of molecules with a sinusoidal field, are discussed by using an expression for the profiles derived in the rotating wave approximation. The validity of this result is discussed with reference to exact two-level model calculations.     

Theoretical study of IR band intensities and electronic transition moments for the β and δ systems of NO

The variation of the electronic transition moment with internuclear separation has been calculated for the beta and delta systems of NO. Theoretical band intensities for the fundamental and first two overtones have also been calculated for the ground state. The results are based on the self-consistent-field plus configuration-interaction technique, and they are compared with the existing experimental data. Theoretical potential-energy curves and the spectroscopic constants T_e, r_e, ω_e, and ω_eχ_e for the X²π, B²π, and C²π electronic states of NO are also reported.