Dipole Flux Research Articles

A Charge-Charge Flux-Dipole Flux Analysis of Simple Molecular Systems with Halogen Bonds.

The presence of halogen bonds (R-X···B; R = substituent group, X = halogen, and B = Lewis base) provides quite amazing molecular systems for electronic structure investigations, presenting unique characteristics of fundamental relevance to supramolecular chemistry among other areas. Here, we use a double-hybrid approach from Density Functional Theory and triple-ζ basis sets augmented with diffuse functions (B2PLYP/def2-TZVPD) to deal with a large group of simple molecular systems containing halogen bonds (XBs), focusing on geometrical structures, binding energies, harmonic vibrational frequencies, and fundamental infrared intensities. Next, the electron densities and their variations on vibrations are carefully studied with the Quantum Theory of Atoms in Molecules (QTAIM) formalism and the charge-charge flux-dipole flux (CCFDF) model. We notice that the R-X stretching mode usually shows vibrational frequency decrements and infrared intensifications during the XB formation. Such features were also observed in hydrogen bonds, although the explanation for the band strengthening is different. Surprisingly, the most important contribution to these intensity increments due to complexation is now the interaction term between the charge flux and dipole flux (CF × DF). Thus, the use of atomic dipoles is mandatory to fully understand this phenomenon. In fact, the huge charge flux contributions to changes in dipole moment derivatives of R-X stretchings on halogen bonding are no longer accompanied by opposite variations of similar magnitudes in polarizations described by atomic dipole fluxes, which provided nearly unaltered values during the XB formation. Thus, the electronic charge flux direction change that takes place in complexes (from B to R) now reinforces dipole moment derivative terms from such atomic polarizations (mainly from the X atom). This intermolecular charge flux seems to be responsible for the unusual features noticed in the R-X stretching mode with the CCDDF/QTAIM model.

Dynamics of ferromagnetic due to nonlinear thermal buoyancy when Cattaneo–Christov heat flux and magnetic dipole whose magnetic scalars are significant

The fluid flow and heat transfer characteristics under magnetic dipole with non-Fourier flux are useful in understanding practical significance for undersea applications, for example, managing transference and/or separation of the boundary layer above submerged blocks and in suppressing recirculating bubbles. The heat transfer features of a ferromagnetic fluid were numerically analyzed over an elastic elongating surface convectively heated. Over a flexible body at the boundary, a partial Casson slip is considered. To balance the heat transition, the radiative and non-Fourier flux are combined in the energy. Similarity modifications are utilized to transform the partial differential equations (PDEs) from linear momentum and traditional energy equations into ordinary differential equations (ODEs) that are nonlinear. By the shooting method, numerical solutions to these equations are obtained. The results of various related physical parameters are studied, including ferromagnetic activity, dimensionless velocity slip, Biot number, thermal radiation, thermal slip, temperature and velocity area instability. The surface friction and the number of Nusselt are also measured for and at separate embedded parameters.

Existence and uniqueness of stationary solutions in $5$-dimensional minimal supergravity

We study the problem of stationary bi-axially symmetric solutions of the $5$-dimensional minimal supergravity equations. Essentially all possible solutions with nondegenerate horizons are produced, having the allowed horizon cross-sectional topologies of the sphere $S^3$, ring $S^1\times S^2$, and lens $L(p,q)$, as well as the three different types of asymptotics. The solutions are smooth apart from possible conical singularities at the fixed point sets of the axial symmetry. This analysis also includes the solutions known as solitons in which horizons are not present but are rather replaced by nontrivial topology called bubbles which are sustained by dipole fluxes. Uniqueness results are also presented which show that the solutions are completely determined by their angular momenta, electric and dipole charges, and rod structure which fixes the topology. Consequently we are able to identify the finite number of parameters that govern a solution. In addition, a generalization of these results is given where the spacetime is allowed to have orbifold singularities.

The Natural Charge – Natural Charge Flux – Overlap model: a modification of the charge-charge flux-overlap model through NPA charges

Some models were developed for the interpretation of infrared intensities based on the distribution of molecular charge and its mobility during atomic displacement. The objective of this paper is to apply NPA charges in the C-CF-O model to obtain the dipole moment derivatives and infrared intensities of AH3, X2CY and some linear molecules. In all cases analyzed, the NC-NCF-O model was more accurate than the reference model Charge – Charge Flux – Dipole Flux (C–CF–DF). Furthermore, the computational cost of obtaining NPA charges and their respective flux are much lower than those obtained by more complex models. This allows a greater application for large molecules.

Low geomagnetic field strength during End-Cretaceous Deccan volcanism and whole mantle convection

Knowledge about long-term variation of the geomagnetic dipole field remains in its nascent stage because of the paucity of reliable experimental data over geological periods. Here, we present the first robust experimental data from the largest Cretaceous flood basalt province on Earth, the ~65–66 Ma Deccan basalt within a thick (1250 m) unbiased stratigraphic section down to the basement, recovered from a drill hole of the Koyna Deep Scientific Drilling Project in the Western Ghats, India. Critical analysis of the result along with similar results of the Cretaceous age find that (i) the dipole moment during the end Cretaceous Deccan eruption is the lowest in whole of Cretaceous (ii) dipole moment at the onset/termination of the Cretaceous Normal Superchron is apparently lower relative to that in mid-superchron, however, such differences cannot be deciphered in shorter polarities probably because of insufficient time to develop recognizable variations (iii) inverse relation between dipole moment and reversal rate is lacking and (iv) a cause and effect relation between core-mantle boundary heat flux and low dipole moment that appears to be the principle governing factor in forming the Large Igneous Provinces on the surface of earth.

Characteristic Substitution Shift Model (CSSM) in the CCFDF (Charge-Charge Flux-Dipole Flux) model for the dipole moment derivatives of molecules X2CY (X = F, cl; Y = O, S)

In the spectroscopic study of the X2CY molecules, the dipole moment derivative model Charge – Charge Flux - Dipole Flux (CCFDF) derived from the QTAIM theory was used to verify if the CSSM (Characteristic Substitute Shift Model) model was adequate to represent the derivatives of the dipole moment of the X2CY molecules. To choose the best level/basis combination, a study varying level electron correlation with different basis set was performed to see which wavefunction best describes the dipole moment of the X2CY molecules. When the derivatives of the dipole moment CCFDF are decomposed into charge, charge flux and dipole flux, the CSSM model perfectly represented the charge component, however, it presented small discrepancies for the charge flux and more significant discrepancies with respect to the dipole flux, due to the difficulty of this model representing the variations of the atomic dipole of the sulfur atom.

Rare palaeomagnetic evidence of long-term mantle control of the geodynamo and possible role of the NAD field in the reversal process

SUMMARY The degree to which the lowermost mantle influences behaviour of the geodynamo has been debated over the past quarter century. Our analysis of a comprehensive set of 17 Cenozoic palaeomagnetic transitional field records obtained from lavas in the Southern Hemisphere provides robust evidence of stable mantle control since the Pliocene. The records come from a region where—given a significantly weakened axial dipole—the magnetic field today would be largely controlled by the non-axial dipole (NAD) flux patch currently emanating from Earth's outer core beneath western Australia. The palaeomagnetic recording sites from west to east include the south Indian Ocean, eastern Australia, New Zealand and French Polynesia. The analysed records contain from 2 to 26 sequential transitional virtual geomagnetic poles (VGPs). 10 of the 17 records supply at least one VGP within a narrow longitudinal band 10°-wide between 60°S and the equator, centred along 102.4°E. That is, transitional data from 59 per cent of the Cenozoic recordings are found to reside in a region that encompasses a mere 2.8 per cent of the VGP transitional area on Earth's surface. A robust Monte Carlo approach applied to this data set, one that takes into account the number of transitional VGPs contained in each record, finds this result highly improbable (p-value = 0.0006). The present-day pattern of vertical flux at the core–mantle boundary shows an anomalously strong, thin Southern Hemisphere longitudinal band off the west coast of Australia that strikingly coincides with this unusual palaeomagnetic finding. We conclude with a high degree of confidence that this band of flux has remained virtually unmoved for at least the past 3 Myr. Seemingly independent of the behaviour of the axial dipole, our findings indicate that it has dominated the magnetic field over an area of considerable size during attempts by the geodynamo to reverse polarity.

Infrared intensity analysis of hydroxyl stretching modes in carboxylic acid dimers by means of the charge-charge flux-dipole flux model.

The Charge-Charge Flux-Dipole Flux (CCFDF) model in terms of multipoles from the quantum theory of atoms in molecules (QTAIM) was used to investigate the variations in infrared intensities of hydroxyl (OH) stretching modes during the dimerization of carboxylic acids. The hydrogen bond formation in these systems results into bathochromic shifts of vibrational frequencies for all the OH stretching modes along with huge infrared intensity increments for some of them. These bands become more intense on dimerization due mainly to changes in the cross-term contribution between charge and charge flux. In addition, interaction energies for the pair of atoms directly involved in individual hydrogen bonds (O…H) are linearly correlated to electron densities at their bond critical points (BCPs). Therefore, the hydrogen bonds between the carbonyl group (CO) of acetic acid and the hydroxyl group of halogenated monomers show the largest electron density values at their BCPs. The formation of these intermolecular interactions is also accompanied by ionic character enhancements of OH bonds and electron density decrements at their BCPs. We finally noticed that the hydrogen atom belonging to the hydroxyl group loses electronic charge, while the oxygen from the CO end becomes more negatively charged during dimerization. © 2019 Wiley Periodicals, Inc.

Low-lying electronic excited states and fundamental infrared intensities for ozone: The QTAIM/CCFDF model

The Charge - Charge Flux - Dipole Flux (CCFDF) model using QTAIM parameters at the SAC-CI/cc-pVTZ calculation level was used to estimate fundamental vibrational intensities for ground and 15 low-lying electronic excited states for Ozone. QTAIM/CCFDF charge and charge flux terms were the most important contributions to both Q1 and Q2 modes. Q3 mode accounted for dipole flux term. Electronic Localization Functions (ELFs) were also employed to interpret some electronic transitions from ground state. Atomic polar tensor elements after geometry reorientation show that charge flux represents the most important contribution to the infrared intensities. These results indicate that QTAIM/CCFDF approach can be employed to interpret infrared intensities not only for ground, but also for electronic excited states.

Real space atomic decomposition of fundamental properties of carbon monoxide in the ground and the two lowest lying excited electronic states

ABSTRACTThe properties of carbon monoxide in its ground and two lowest lying excited states are investigated by conventional and time-dependent (TD) density functional theory (DFT). The dipole moment is decomposed into atomic polarisation (AP) and inter-atomic charge transfer (CT) contributions according to the quantum theory of atoms in molecules (QTAIM). Considerable AP and CT contributions cancel in the ground state (S0) resulting in its known negligible dipole moment. This balance is disturbed in the lowest triplet (T1) and singlet (S1) excited states, resulting in dipole moments of 1.57 D for T1 and 0.49 D for S1 . The AP decreases by 2.5 D on excitation to either state but the opposing CT is reduced by 0.8 D for T1 and by 1.8 D for S1, insufficient for cancellation. These excitations induce charge transfer from O to C which drives dipole changes accompanied by a weakening of the C–O bond, more pronounced in the S1 state, as trends in bond lengths, vibrational frequencies, and QTAIM properties suggest. The charge–charge flux–dipole flux (CCFDF) model in terms of QTAIM parameters reveals that the vibrational stretching band weakening on excitation is predominantly due to changes in atomic charges.

Anomalous Fraunhofer interference in epitaxial superconductor-semiconductor Josephson junctions

We investigate patterns of critical current as a function of perpendicular and in-plane magnetic fields in superconductor-semiconductor-superconductor (SNS) junctions based on InAs/InGaAs heterostructures with an epitaxial Al layer. This material system is of interest due to its exceptionally good superconductor-semiconductor coupling, as well as large spin-orbit interaction and g-factor in the semiconductor. Thin epitaxial Al allows the application of large in-plane field without destroying superconductivity. For fields perpendicular to the junction, flux focusing results in aperiodic node spacings in the pattern of critical currents known as Fraunhofer patterns by analogy to the related interference effect in optics. Adding an in-plane field yields two further anomalies in the pattern. First, higher order nodes are systematically strengthened, indicating current flow along the edges of the device, as a result of confinement of Andreev states driven by an induced flux dipole; second, asymmetries in the interference appear that depend on the field direction and magnitude. A model is presented, showing good agreement with experiment, elucidating the roles of flux focusing, Zeeman and spin-orbit coupling, and disorder in producing these effects.

Variations of solar, interplanetary, and geomagnetic parameters with solar magnetic multipole fields during Solar Cycles 21–24

In this study we compare the temporal variations of the solar, interplanetary, and geomagnetic (SIG) parameters with that of open solar magnetic flux from 1976 to 2012 (from Solar Cycle 21 to the early phase of Cycle 24) for a purpose of identifying their possible relationships. By the open flux, we mean the average magnetic field over the source surface (2.5 solar radii) times the source area as defined by the potential field source surface (PFSS) model of the Wilcox Solar Observatory (WSO). In our result, most SIG parameters except the solar wind dynamic pressure show rather poor correlations with the open solar magnetic field. Good correlations are recovered when the contributions from individual multipole components are counted separately. As expected, solar activity indices such as sunspot number, total solar irradiance, 10.7cm radio flux, and solar flare occurrence are highly correlated with the flux of magnetic quadrupole component. The dynamic pressure of solar wind is strongly correlated with the dipole flux, which is in anti-phase with Solar Cycle (SC). The geomagnetic activity represented by the Ap index is correlated with higher order multipole components, which show relatively a slow time variation with SC. We also found that the unusually low geomagnetic activity during SC 23 is accompanied by the weak open solar fields compared with those in other SCs. It is argued that such dependences of the SIG parameters on the individual multipole components of the open solar magnetic flux may clarify why some SIG parameters vary in phase with SC and others show seemingly delayed responses to SC variation.

Atomic charge transfer-counter polarization effects determine infrared CH intensities of hydrocarbons: a quantum theory of atoms in molecules model.

Atomic charge transfer-counter polarization effects determine most of the infrared fundamental CH intensities of simple hydrocarbons, methane, ethylene, ethane, propyne, cyclopropane and allene. The quantum theory of atoms in molecules/charge-charge flux-dipole flux model predicted the values of 30 CH intensities ranging from 0 to 123 km mol(-1) with a root mean square (rms) error of only 4.2 km mol(-1) without including a specific equilibrium atomic charge term. Sums of the contributions from terms involving charge flux and/or dipole flux averaged 20.3 km mol(-1), about ten times larger than the average charge contribution of 2.0 km mol(-1). The only notable exceptions are the CH stretching and bending intensities of acetylene and two of the propyne vibrations for hydrogens bound to sp hybridized carbon atoms. Calculations were carried out at four quantum levels, MP2/6-311++G(3d,3p), MP2/cc-pVTZ, QCISD/6-311++G(3d,3p) and QCISD/cc-pVTZ. The results calculated at the QCISD level are the most accurate among the four with root mean square errors of 4.7 and 5.0 km mol(-1) for the 6-311++G(3d,3p) and cc-pVTZ basis sets. These values are close to the estimated aggregate experimental error of the hydrocarbon intensities, 4.0 km mol(-1). The atomic charge transfer-counter polarization effect is much larger than the charge effect for the results of all four quantum levels. Charge transfer-counter polarization effects are expected to also be important in vibrations of more polar molecules for which equilibrium charge contributions can be large.

Quantum Theory of Atoms in Molecules/Charge–Charge Flux–Dipole Flux interpretation of fundamental vibrational intensity enhancements on H-bond formation of water trimer

The Quantum Theory Atoms in Molecules/Charge–Charge Flux–Dipole Flux model was used to investigate electronic structure variations associated with intensity changes for water trimer vibrations. The total of 440kmmol−1 experimental intensity for the symmetric stretches amounts to an average contribution of 147kmmol−1 per hydrogen bond. The calculated QCISD/cc-pVTZ value is 274kmmol−1. The largest changes on complex formation occur for the charge, charge flux and their interaction. The hydrogen-bonded hydrogen atoms account for 99% of the total intensity of the two strongest symmetric stretches, mostly owing to mechanical vibration factors.

Quantum theory of atoms in molecules/charge-charge flux-dipole flux models for fundamental vibrational intensity changes on H-bond formation of water and hydrogen fluoride

The Quantum Theory of Atoms In Molecules/Charge-Charge Flux-Dipole Flux (QTAIM/CCFDF) model has been used to investigate the electronic structure variations associated with intensity changes on dimerization for the vibrations of the water and hydrogen fluoride dimers as well as in the water-hydrogen fluoride complex. QCISD/cc-pVTZ wave functions applied in the QTAIM/CCFDF model accurately provide the fundamental band intensities of water and its dimer predicting symmetric and antisymmetric stretching intensity increases for the donor unit of 159 and 47 km mol(-1) on H-bond formation compared with the experimental values of 141 and 53 km mol(-1). The symmetric stretching of the proton donor water in the dimer has intensity contributions parallel and perpendicular to its C2v axis. The largest calculated increase of 107 km mol(-1) is perpendicular to this axis and owes to equilibrium atomic charge displacements on vibration. Charge flux decreases occurring parallel and perpendicular to this axis result in 42 and 40 km mol(-1) total intensity increases for the symmetric and antisymmetric stretches, respectively. These decreases in charge flux result in intensity enhancements because of the interaction contributions to the intensities between charge flux and the other quantities. Even though dipole flux contributions are much smaller than the charge and charge flux ones in both monomer and dimer water they are important for calculating the total intensity values for their stretching vibrations since the charge-charge flux interaction term cancels the charge and charge flux contributions. The QTAIM/CCFDF hydrogen-bonded stretching intensity strengthening of 321 km mol(-1) on HF dimerization and 592 km mol(-1) on HF:H2O complexation can essentially be explained by charge, charge flux and their interaction cross term. Atomic contributions to the intensities are also calculated. The bridge hydrogen atomic contributions alone explain 145, 237, and 574 km mol(-1) of the H-bond stretching intensity enhancements for the water and HF dimers and their heterodimer compared with total increments of 149, 321, and 592 km mol(-1), respectively.

An atom in molecules study of infrared intensity enhancements in fundamental donor stretching bands in hydrogen bond formation.

Vibrational modes ascribed to the stretching of X-H bonds from donor monomers (HXdonor) in complexes presenting hydrogen bonds (HF···HF, HCl···HCl, HCN···HCN, HNC···HNC, HCN···HF, HF···HCl and H2O···HF) exhibit large (4 to 7 times) infrared intensity increments during complexation according to CCSD/cc-pVQZ-mod calculations. These intensity increases are explained by the charge-charge flux-dipole flux (CCFDF) model based on multipoles from the Quantum Theory of Atoms in Molecules (QTAIM) as resulting from a reinforcing interaction between two contributions to the dipole moment derivatives with respect to the vibrational displacements: charge and charge flux. As such, variations that occur in their intensity cross terms in hydrogen bond formation correlate nicely with the intensity enhancements. These stretching modes of HXdonor bonds can be approximately modeled by sole displacement of the positively charged hydrogens towards the acceptor terminal atom with concomitant electronic charge transfers in the opposite direction that are larger than those occurring for the H atom displacements of their isolated donor molecules. This analysis indicates that the charge-charge flux interaction reinforcement on H-bond complexation is associated with variations of atomic charge fluxes in both parent molecules and small electronic charge transfers between them. The QTAIM/CCFDF model also indicates that atomic dipole flux contributions do not play a significant role in these intensity enhancements.

QTAIM charge–charge flux–dipole flux models for the fundamental infrared intensities of BF3 and BCl3

Quantum Theory of Atoms in Molecules Charge–Charge Flux–Dipole Flux (QTAIM/CCFDF) models have been determined for the BF3 and BCl3 molecules. Model parameters were obtained from MP2/6–31G(2d,2p) wave functions owing to their accurate estimations of the BF3 intensities and were found to be insensitive to changes in basis sets with polarization functions and to the level of electron correlation treatment, MP2, QCISD and DFT. The BF3 stretching intensity has a very dominant equilibrium charge contribution with small charge and dipole fluxes occurring in the opposite direction to the charge movement. Large equilibrium charge and small dynamic contributions are also characteristic of stretching vibrations in the ionic diatomic molecules, NaF, NaCl, LiF and LiCl. Furthermore the Laplacians of the electron density at the bond critical points of BF3 and these diatomics are all positive indicating electron depletion in their bonding regions relative to large electronic densities concentrated around their nuclei that is characteristic of ionic bonds. The MP2/6–31G(2d,2p) BCl3 stretching intensity can be accurately estimated by equilibrium charge movement since the charge and dipole fluxes almost exactly cancel one another. Both in-plane and out-of-plane BF3 and BCl3 bending deformations are described by equilibrium charge movements that are partially canceled by opposing dipole fluxes that measure the effect on the dipole moment change from electron densities polarized in the opposite direction. Charge fluxes are calculated to be small for the in-plane deformations and are zero by symmetry for the out-of-plane ones.

A theoretical systematic study of a series of isocyanopolyynes

Several isocyanopolyynes, HCnNC (n=0, 2,…,16), are analyzed in this theoretical work. We performed calculations at MP2/cc-pVTZ (n=0–16), CCSD/cc-pVDZ (n=0–12) and CCSD/cc-pVTZ (n=0–6) levels. The dipole moments from the best treatment, CCSD/cc-pVTZ, are in much closer agreement with those obtained in CCSD/cc-pVDZ calculations (deviations up to 0.05 Debye) than with the results from MP2/cc-pVTZ (discrepancies that can reach 0.55 Debye). Moreover, the CCSD/cc-pVTZ level yields values in excellent accordance with experimental dipole moments for HNC and HC2NC. Hence, this allows concluding that the correct treatment of electron correlation is more important than increments in basis sets for this electric property in isocyanopolyynes and CCSD/cc-pVDZ values are indicated as the best estimates available for large isocyanopolyynes. The findings from infrared intensities of fundamental vibrational bands are also similar (mean deviations of 3.1kmmol−1 for CCSD/cc-pVDZ and 12.6kmmol−1 for MP2/cc-pVTZ with respect to CCSD/cc-pVTZ results). Thus, we decided to use the charge – charge flux – dipole flux (CCFDF) model from multipoles given by the Quantum Theory of Atoms in Molecules (QTAIM), which were obtained at the CCSD/cc-pVDZ level, to investigate the variations in infrared intensities of some selected modes along these systems. The intensity of the band associated with CH stretching shows an increase with the size of these molecules (from 96 to 146kmmol−1 between n=4 and 12) that is readily explained by variations in the charge flux contribution to this mode, in a similar way as found before for cyanopolyynes. Furthermore, the degenerate CH bending vibrations present almost constant intensities in these isocyanopolyynes (around 37–38kmmol−1 from n=4 up to n=12) and this pattern is supported by CCFDF/QTAIM contributions. The band mostly assigned to stretching of the NC triple bond, which can also be described as asymmetric stretching mode of all pairs of adjacent triple bonds, shows an increase of intensity up to n=6 and is associated to values around 96–102kmmol−1 in the remaining larger members. Another important mode detected is a symmetric stretching of NC and CC triple bonds belonging to the isonitrile end (between 66 and 101kmmol−1 when n=6–12) for which the charge contribution is nearly constant and dynamic contributions change in a more complicated way. The most intense fundamental band in each isocyanopolyyne from n=4 to 12 is assigned to vibrations of triple bonds in both ends of these systems (from 129 to 164kmmol−1) and an alternating behavior according with even or odd numbers of CC triple bonds is observed for these values and also for respective CCFDF/QTAIM contributions. Finally, this work also brings values derived from regressions that are indicated as the best estimates of rotational constants and dipole moments to be used for detection of large isocyanopolyynes in the interstellar medium.

Atomic charge and atomic dipole fluxes during stretching displacements in small molecules

First, the convergence in values of dynamic quantities such as atomic charge flux and atomic dipole flux that take place in stretching displacements is investigated in this work by means of calculations with three basis sets (cc-pVDZ, cc-pVTZ and cc-pVQZ) and different theoretical methods (HF, MP2, MP4(SDQ) and CCSD). The charges were obtained from QTAIM, Mulliken and NPA formalisms while atomic dipoles are only calculated from QTAIM. We studied a group of simple diatomic and triatomic molecules with diverse chemical bonding character: HF, HCl, LiH, NaH, NaCl, LiF, NaF, BF, AlF, BeO, MgO, CO, ClF, HCN, HNC, OCS, CO2 and CS2. The data obtained indicate that these dynamic quantities show well-behaved convergence patterns except by those from Mulliken for some triatomic systems with increasing basis set size. Some relevant dependence of QTAIM fluxes was observed in HF and HNC when small basis sets are used but the results still converge when larger basis sets are employed. Moreover, charge fluxes from QTAIM are in nice accordance with chemical arguments while the other formalisms exhibit results that are not plausible in some cases. The most remarkable ones are noticed in highly ionic diatomic systems, which should present negligible charge flux values during bond stretching displacements around equilibrium geometries.

How Accessible Is Atomic Charge Information from Infrared Intensities? A QTAIM/CCFDF Interpretation

Infrared fundamental intensities calculated by the quantum theory of atoms in molecules/charge-charge flux-dipole flux (QTAIM/CCFDF) method have been partitioned into charge, charge flux, and dipole flux contributions as well as their charge-charge flux, charge-dipole flux, and charge flux-dipole flux interaction contributions. The interaction contributions can be positive or negative and do not depend on molecular orientations in coordinate systems or normal coordinate phase definitions, as do CCFDF dipole moment derivative contributions. If interactions are positive, their corresponding dipole moment derivative contributions have the same polarity reinforcing the total intensity estimates whereas negative contributions indicate opposite polarities and lower CCFDF intensities. Intensity partitioning is carried out for the normal coordinates of acetylene, ethylene, ethane, all the chlorofluoromethanes, the X(2)CY (X = F, Cl; Y = O, S) molecules, the difluoro- and dichloroethylenes and BF(3). QTAIM/CCFDF calculated intensities with optimized quantum levels agree within 11.3 km mol(-1) of the experimental values. The CH stretching and in-plane bending vibrations are characterized by significant charge flux, dipole flux, and charge flux-dipole flux interaction contributions with the negative interaction tending to cancel the individual contributions resulting in vary small intensity values. CF stretching and bending vibrations have large charge, charge-charge flux, and charge-dipole flux contributions for which the two interaction contributions tend to cancel one another. The experimental CF stretching intensities can be estimated to within 31.7 km mol(-1) or 16.3% by a sum of these three contributions. However, the charge contribution alone is not successful at quantitatively estimating these CF intensities. Although the CCl stretching vibrations have significant charge-charge flux and charge-dipole flux contributions, like those of the CF stretches, both of these interaction contributions have opposite signs for these two types of vibrations.