Polarizability of molecular clusters as calculated by a dipole interaction model

We have investigated different models for parameterizing the frequency-dependent molecular polarizability. The parameterization is based on an electrostatic model for interacting atoms and includes atomic polarizabilities, atom-type parameters describing the damping of the electric fields and the frequency dependence. One set of parameters has been used for each element. The investigation has been carried out for 115 molecules with the elements H, C, N, O, F, and Cl, for which the frequency-dependent polarizability tensor has been calculated with ab initio methods. We find that the static polarizability of aliphatic and aromatic compounds can be described with the same set of parameters. The conclusion is that a simple electrostatic model to a good degree can model the essential behavior of the frequency-dependent molecular polarizability.

A specific method, combining some ingredients of the well-known DDA and PDI approaches, has been developed in our group since many years to calculate the absorption cross-sections of carbonaceous nanoparticles based on their atomistic details. This method, here named the Dynamic Atomic Dipole Interaction (DADI) model, requires the knowledge of the position and frequency-dependent polarizability of each atom constituting the nanoparticles. While the atomic positions can be quite easily obtained, for example as the results of molecular dynamics simulations, obtaining the frequency-dependent atomic polarizabilities is a trickier task. Here, a fitting procedure, named the reverse-DADI method, has been applied to calculate the frequency-dependent atomic polarizability values for carbon and hydrogen atoms involved in aromatic cycles or in aliphatic chains, on the basis of frequency-dependent molecular polarizabilities of various PAH and alkane molecules, calculated with the TD-DFT theory, in the UV–Visible range. Then, using these frequency-dependent atomic polarizabilities as input parameters in the DADI model has been shown to lead to an accurate representation of the absorption cross-sections of various PAH and alkane molecules with respect to the corresponding values obtained at the TD-DFT level, with however the great advantage of a much shorter time of calculations. Furthermore, these results are indications of a good transferability of the frequency-dependent atomic polarizability values obtained here to any C or H atom of any PAH or alkane molecule. This opens the way for building large databases of optical properties for carbonaceous species of atmospheric or astrophysical interests.

In view of the experimental observation of (H2)2@C70 and (H2O)2@C70, it has been suggested that hydrogen fluoride (HF) dimer can be completely localized within the sub-nanospace inside the fullerene C70 cage. With the aim of quantum chemical prospective of (HF)2@C70, electronic structure calculations of C60 hosting H2, HF, and H2O monomers, as well as C70 hosting H2, HF, and H2O monomers and dimers, were performed by using the density functional theory, together with the quantum theory of atoms in molecules, the natural population, and interaction energy calculation. The F–H···F bonding energy inside C70 was estimated at −13.25 kcal/mol, which is smaller than that of free dimer in the gas phase (−8.37 kcal/mol). Exploration of various featured properties suggests that (HF)2@C70 may be also regarded as a unique system composed of both inter- and intramolecular interactions like (H2)2@C70 and (H2O)2@C70. In addition, absorption spectroscopy and linear and nonlinear optical coefficients of C60 hosting H2, HF...

Low-wavenumber vibrational dynamics are studied for liquid formamide (FA) and N-methylformamide (NMF) by the methods of molecular dynamics (MD) and instantaneous normal mode (INM) analysis. The dipole-induced dipole (DID) mechanism is employed for calculating polarizability tensors, the correlation function of which determines Raman spectral profiles and optical Kerr effect (OKE) responses. It is shown that the calculated Raman spectra and OKE responses are in reasonable agreement with those observed in previous studies. The main features of these optical signals are explained by simple librations of the unperturbed molecular polarizability (UMP) tensors, which are considerably anisotropic, although the intensities of the librational components are enhanced to some extent by intermolecular interactions, especially in the case of liquid NMF. The DID term gives rise to smaller intensities in a lower wavenumber region than the UMP term. It is suggested that these features of the optical signals may be regarded as characteristic of strongly interacting liquids with substantial anisotropy in molecular polarizability tensors. It is also shown that the marked difference between the Raman spectra of liquid FA and NMF in the low-wavenumber region arises from a difference in the librations of these molecules around the longer in-plane molecular axis of inertia. The difference is related to the dimensionality of hydrogen bonding in the liquids: two-dimensional in liquid FA and one-dimensional in liquid NMF.

In this paper the eigenmodes of finite length microring resonator arrays have been systematically studied, both analytically using temporal coupled mode theory (CMT), and numerically using two-dimensional finite element method (FEM). The method for obtaining the values of parameters appearing in simplified CMT model using results of FEM calculations is presented. Calculations were carried out by COMSOL FEM packages for a wide range of distances between the rings. The obtained results reveal that the rotational degeneracy is preserved for a wide range of interrings distances. It is shown how the eigenvalue spectrum depends on the number of cavities in the system. The differences for the cases of odd and even numbers of rings, and its implications on actual applications, are discussed in details. The central branch appearing in odd-number arrays plays significant role for the delay-lines and optical buffering applications. Based on the first order perturbation theory, an analytical expressions for the eigenfrequencies of arbitrary (finite) length linear array of microring resonators are derived. The analytical expressions describing eigenfrequencies are useful for determining positions of the maxima in transfer characteristics in microring arrays with external buses.

Polarizability of silicon clusters

The point dipole interaction model for molecular polarizability proposed by Applequist, Carl, and Fung [J. Am. Chem. Soc. 94, 2952 (1972)] is modified by replacing the point dipole interaction tensor with a descaled distributed charge interaction tensor. Our procedure is based on the descaled tensor algorithm proposed by Thole [Chem. Phys. 59, 341 (1981)] and uses a Slater-type orbital (STO) function to represent the charge distribution. The resulting STOPDI formalism calculates mean molecular polarizabilities and the components of the molecular polarizabilities with errors comparable to experimental uncertainty. Furthermore, these procedures require only one optimized parameter per atom, the average atomic polarizability. The formalism is invariant to coordinate transformations and avoids the discontinuities and/or false resonances that are characteristic of previous classical and semiclassical formalisms. The STOPDI algorithm requires less parameterization and computation time than the anisotropic atom point dipole interaction (AAPDI) model of Birge [J. Chem. Phys. 72, 5312 (1980)] and is more reliable for the calculation of polarizability derivatives and Raman cross sections. We demonstrate, however, that none of the above formalisms are reliable for calculating absolute Raman cross sections for normal modes involving significant bond stretching components. This is an inherent limitation of any formalism which does not explicitly account for electron density redistribution accompanying changes in the internuclear distances of covalently bonded atoms.

• Provides a practical tool for choosing the best CO₂ transport option in CCUS systems. • Step-by-step cost calculation approach for CO₂ transport by truck. • Identifies cost thresholds for switching from trucking to pipelines: trucking is least-cost up to 400 t/d. • OPEX dominates CAPEX; energy and O&M form 60 % of total operating costs. • Sensitivity analysis highlights trailer capacity and electricity price impacts. This study presents a techno-economic evaluation of liquefied CO 2 transport via trucking, covering the full transport chain from liquefaction, buffer storage and trucking to reconditioning. The analysis spans a wide range of transport demands (25–1000 t/d) and distances (25–500 km), aiming to quantify the conditions under which trucking is a cost-effective alternative to pipeline transport. A detailed cost model was developed for each transport stage, including component-level capital and operating costs. Results indicate that trucking transport is economically favorable for long distances and low transport volumes, with its cost advantage ending beyond 400 t/d. As distance increases, trucking remains competitive at higher flow rates up to this threshold. Liquefaction is the dominant cost contributor at shorter distances, whereas the trucking part becomes the largest cost factor over longer distances. Buffer storage and reconditioning consistently contribute less to the total cost. Operational expenditure (OPEX) consistently exceeds capital expenditure (CAPEX), with energy consumption and liquefaction O&M costs together representing on average around 60% of OPEX (ranging from ∼80% for the 50 km case to ∼43% for the 500 km case). The Sensitivity analysis identifies trailer load capacity and electricity price as the most influential cost drivers, while fixed infrastructure costs have relatively minor impacts. Overall, this work provides a robust framework and practical insights for selecting cost-efficient CO 2 transport methods and supports future planning of CCUS systems. Beyond its quantitative findings, this study introduces a transparent, step-by-step methodology for CO 2 trucking cost assessment, filling a notable gap in existing literature.

Detection and classification of bottom-laid targets in littoral area represents a serious problem for the navies of the world. It has been shown based on past acoustic research that the backscattered field carries a lot of information about the subject in terms of frequency and angular distribution if ensonified over a wide range of distance and can thus be used to different a mine from a stone or one type of mine from the other, referred to as acoustic color image. A circular array is more advantageous compared to a planar array as circular patterns maximize the aperture，and due to its high angular resolution, one can search and classify multiple targets at the same time. While it is difficult to deploy a large circular array since one does not know where is the target and the circular array needs to have a large diameter. Therefore, in this work, one will demonstrate effective bottom-laid targets imaging and classification using a synthetic circular array, which is created by a towed line array. We will study the concept of the proposed system and make simplified assumptions in order to obtain a crude estimate of the system performance.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 197573, “Asset Value Maximization Through a Novel Well-Completion System for 3D Time-Lapse Electromagnetic Tomography Supported by Machine Learning,” by Paolo Dell’Aversana, Raffaele Servodio, and Franco Bottazzi, Eni, et al., prepared for the 2019 Abu Dhabi International Petroleum Exhibition and Conference, Abu Dhabi, 11–14 November. The paper has not been peer reviewed. In this paper, the authors introduce a new technology installed permanently on the well completion and addressed to real-time reservoir fluid mapping through time-lapse electromagnetic tomography during production or injection. The variations of the electromagnetic fields caused by changes of the fluid distribution are measured in a wide range of distances from the well. The data are processed and interpreted through an integrated software platform that combines 3D and 4D geophysical data inversion with a machine-learning (ML) platform. The complete paper clarifies the details of the ML work flow applied to electrical resistivity tomography (ERT) models using an example based on synthetic data. Introduction An important question in well completions is how one may acquire data with sufficient accuracy for detecting the movements of the fluids in a wide range of distances in the space around the production well. One method that is applied in various Earth disciplines is time-lapse electrical resistivity. The operational effectiveness of ERT allows frequent acquisition of independent surveys and inversion of the data in a relatively short time. The final goal is to create dynamic models of the reservoir supporting important decisions in near-real-time regarding production and management operations. ML algorithms can support this decision-making process. Methodology In a time-lapse ERT survey [often referred to as a direct-current (DC) time-lapse survey], electrodes are installed at fixed locations during monitoring. First, a base resistivity data set is collected. The inversion of this initial data set produces a base resistivity model to be used as a reference model. Then, one or more monitor surveys are repeated during monitoring. The same acquisition parameters applied in the base survey must be used for each monitor survey. The objective is to detect any small change in resistivity, from one survey to another, inside the investigated medium. As a first approach, the eventual variations in resistivity can be retrieved through direct comparison between the different inverted resistivity models. A different approach is called difference inversion. Instead of inverting the base and monitor data sets separately, in difference inversion, the difference between the monitor and base data sets is inverted. In this way, all the coherent inversion artifacts may be canceled in the difference images resulting from this type of inversion. Repeating the measurements many times (through multiple monitor surveys) in the same area and inverting the differences between consecutive data sets results in deep insight about relevant variations of physical properties linked with variations of the electric resistivity.

Extended calculations of molecular electric dipole polarizability tensor, at Hartree-Fock and correlated level of accuracy (MP2, CCS, CC2, CCSD, and CCSD(T)) have been carried out to investigate whether aromaticity could be related to the electric dipole polarizability of planar ring systems. The calculations prove the exaltation of the average property of conjugated molecules, which is possibly due to their easily polarizable π-electron cloud. On the other hand, theoretical out-of-plane polarizability components are smaller in benzene than in any other C$_6$H$_6$ isomer. The aromatic stabilization energies of monosubstituted five-membered conjugated cyclic molecules increase in the same direction as theoretical out-of-plane polarizabilities.

A many-body version of the symmetry-adapted perturbation theory is developed for a direct calculation of intermolecular potentials as a sum of the electrostatic, exchange, induction, and dispersion contributions. Since no multipole expansion is used, the obtained interaction energy components are properly dampened at short distance by the charge-overlap (penetration) effects. The influence of the intramonomer correlation is accounted for by the perturbation expansion in terms of the Mo/ller–Plesset type fluctuation potentials WA and WB for the individual molecules. For the electrostatic and for the dispersion energy, the terms of the zeroth, first, and second order in WA+WB are considered. In this way, the leading three-particle correlation contribution to the dispersion energy is taken into account. As a test of our method, we have performed calculations of the interaction energy for the water and hydrogen fluoride dimers. Both the geometry and the basis set dependence of the interaction energy components have been investigated. For a comparison, we have also computed the supermolecular interaction energies through the full fourth order of the many-body perturbation theory. On the basis of our results, we predict the association energy for (H2O)2 equal to −4.7±0.2 kcal/mol in relatively poor agreement with the experimental value of −5.4±0.7 kcal/mol, but still within the experimental error bars. For (HF)2, the predicted association energy is −4.2±0.2 kcal/mol, while the experimental value (corrected by a theoretical zero-point energy) is −4.9±0.1 kcal/mol.

Subject and Purpose. The directivity characteristics of a dipole antenna when it is placed above and parallel to a perfectly conducting screen of rectangular shape are considered, aiming to theoretically study dipole antennas with sector-shaped radiation patterns (RP) formed by choosing the optimal electrical dimensions of the screen and the distance between the dipole and the screen. Methods and Methodology. The problem of the dipole radiation field diffraction by the edges of a rectangular screen is solved by the method of the uniform geometric theory of diffraction. The diffracted fields developed at the screen edges are calculated using the uniform asymptotics obtained from the rigorous solution of the model problem of the dipole field diffraction by the edge of a perfectly conducting half-plane. Results. The algorithms and calculation programs developed allow studying the electrodynamic characteristics of the antenna over a wide range of screen electrical dimensions and distances between the dipole and the screen. Radiation patterns, directivity in a path normal to the screen and in directions of maximum radiation, radiation resistance, and protective ratio have been calculated across a broad range of screen dimensions and distances between the dipole and the screen. It has been observed that the antenna of the kind forms sector-shaped radiation patterns when the distance between the dipole and the screen is 0.30 to 0.45 of the resonant wavelength of the dipole. The obtained results have been confirmed by the calculations using the FEKO program. Conclusions. It has been shown that the considered dipole antenna forms sector-shaped radiation patterns when the distance between the dipole and the screen is 0.30 to 0.45 of the dipole resonant wavelength depending on the screen dimensions. The obtained calculation results for the maximum achievable electrodynamic characteristics allow us to find optimal geometric parameters of the antenna with a sector-shaped pattern for a particular application.

Based on the method of approximation of the poles and residues of the polarization propagator in the first-order multireference perturbation theory, a software package was developed, which was applied to calculate the characteristics of transitions from the ground state to 23 excited electronic states of the CH+ ion in a range of internuclear distances R from 0.5 to 10 a.u. A comparison of the determined estimates of the transition energies with the results of calculations by means of the full configuration interaction method in the selected DZ orbital basis gives reasons to consider a balanced approximation of the energies of valence-type electronic transitions to be attainable with our method at a fixed value of R and when it is varied over a wide range. This conclusion does not apply to the estimates of the transition probabilities with our method.

The present study focusses on presenting a global picture to theoretically describe the singly- and doubly-excited states of molecular hydrogen. The non-iterative eigenchannel R-matrix method and multichannel quantum defect theory have been combined for understanding the physics of the wide range of energy and internuclear distances in a unified manner. In this dissertation ab initio calculations for $\sp{1}\Sigma\sb{g}$, $\sp3\Sigma\sb{g}$, $\sp1\Sigma\sb{u}$ and $\sp3\Sigma\sb{u}$ symmetries of hydrogen molecule are performed to test the present approach. The body-frame quantum defects are expected to be mild on energy, but found to be strongly dependent on both energy and internuclear distances in this problem. The energy-independent $\Gamma\sp\prime$ and $\Lambda$ matrices in the eigenchannel R-matrix formulation are interpolated for the internuclear distance variance. The streamlined treatment of eigenchannel R-matrix theory is also adapted for fine energy meshes of calculation. Seven bound states per each symmetry are calculated simultaneously in addition to the doubly excited states based on same matrices $\Gamma\sp\prime$ and $\Lambda$ in non-iterative eigenchannel R-matrix formulation. The global picture for each symmetry is presented, and this tells the interactions between singly- and doubly-excited states. The interactions of the doubly-excited states affect the potential curves of the bound states, and result in many double minimum potentials.