Charge-dipole model to compute the polarization of fullerenes (original) (raw)
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Physical Review B, 2007
We present a model for the calculation of the polarization properties of fullerenes and carbon nanotubes. This model describes each atom by both a net electric charge and a dipole. Compared to dipole-only models, the consideration of electric charges enables one to account for the displacement of free electrons in structures subject to an external field. It also enables one to account for the accumulation of additional charges. By expressing the electrostatic interactions in terms of normalized propagators, the model achieves a better consistency as well as an improved stability. In its most elementary form, the model depends on a single adjustable parameter and provides an excellent agreement with other experimental and theoretical data. The technique is applied to a C 720 fullerene and to open and closed ͑5,5͒ nanotubes. The simulations demonstrate the improved stability of our algorithm. In addition, they quantify the role of free charges in the polarization of these structures. The paper finally investigates the field-enhancement properties of open and closed ͑5,5͒ nanotubes.
A charge-dipole model to compute the polarizability of fullerenes and carbonna notubes
Recent Progress in Computational Sciences and Engineering (2 vols), 2006
We present a model for the calculation of the polarization properties of fullerenes and carbon nanotubes. This model describes each atom by both a net electric charge and a dipole. Compared to dipole-only models, the consideration of electric charges enables one to account for the displacement of free electrons in structures subject to an external field. It also enables one to account for the accumulation of additional charges. By expressing the electrostatic interactions in terms of normalized propagators, the model achieves a better consistency as well as an improved stability. In its most elementary form, the model depends on a single parameter and provides an excellent agreement with other experimental/theoretical data. Compared to dipole-only models, the technique improves the calculation of the local fields. It also quantifies the role of free charges in the polarization of fullerenes and carbon nanotubes.
The Journal of Physical Chemistry A, 2008
We present an electrostatic interaction model for the calculation of the static electronic polarization of hydrocarbons. In previous work, models have often been presented for one single type of hydrocarbons. Here, we discuss the different requirements for a model to describe aliphatic, olephinic, and aromatic systems. The model is based on the representation of the carbon and hydrogen atoms by induced electric charges and dipoles, where the actual values of the charges and dipoles are those that minimize the electrochemical energy of the molecule. The electrostatic interactions are described in terms of normalized propagators, which improves both the consistency and the numerical stability of the technique. For the calibration of our model, we sought at reproducing the molecular polarizabilities obtained by current density functional theory for a set of 48 reference structures. We propose parameters for each type of hydrocarbon, which provide an excellent agreement with the reference data (relative error on the mean molecular polarizabilities of 0.5, 1.4, and 1.9% for alkanes, alkenes, and aromatic molecules, respectively). We also propose parameters based on the local environment of each atom, which are better suited for the description of more complex molecules. We finally study the polarizability of fullerenes and small hydrogen-terminated (5,5) carbon nanotubes.
Polarizabilities, charge states, and vibrational modes of isolated fullerene molecules
Physical Review B, 1992
We have used our local-orbital cluster codes to perform detailed density-functional-based calculations on isolated C60 molecules. We present firstand second-electron affinities, which include all effects due to spin polarization and charge-induced geometrical relaxation. The effects due to the generalized gradient approximation are reported as well. The two Ag and single A"vibrational modes are presented and frequency shifts due to charging are estimated. By placing the fullerene molecules in a static electric field of variable strength, the molecular static polarizabilities are obtained. In comparison to isolated carbon atoms, we find enhancements in the linear polarizabilities due to the delocalized electrons at the Fermi level, but do not observe any large nonlinear static contributions. By including effects due to charge transfer, on-site geometric relaxation, and fullerene polarization, we introduce a simple potential that accounts for long-range interactions and predict Hubbard parameters as a function of alkali-dopant concentration.
Partial Atomic Charges and Screened Charge Models of the Electrostatic Potential
2012
This supporting information was prepared on March 11, 2012 and consists of 10 pages. We calculated the charges, dipole moments, all , and outer of several molecules. Tables S1-S3 show the results of 3 charged molecules without s-block and d-block elements, and Tables S4-S17 show the results of 14 molecules that contain s-block and d-block elements. All electrostatic potentials are from M06/def2-TZVP calculations.
Multiconfigurational Study of the Electronic Structure of Negatively Charged Fullerens
Journal of Chemistry and Chemical Engineering
Multiconfigurational second order perturbation theory was employed in order to describe the ground and excited states of. Different choices of the active spaces are discussed and the possibility to apply multiconfigurational theory to study is investigated. The calculations were performed for all possible spin states (for selected charge) and show the preference of low spin state. The energy difference between two and pairs-and-shows that the probability to create a charge alternation in fullerides is small.
The Static Polarizability and Second Hyperpolarizability of Fullerenes and Carbon Nanotubes †
The Journal of Physical Chemistry A, 2004
Utilizing a point-dipole interaction model, we present an investigation of the static polarizability and second hyperpolarizability of fullerenes and carbon nanotubes by varying their structure. The following effects are investigated: (1) the length dependence of the components of the static polarizability, (2) the static second hyperpolarizabilities of C 60 and C 70 , (3) the symmetry effects on the static second hyperpolarizability, (4) the length dependence of the components of the static second hyperpolarizability, and (5) the diameter dependence of the static second hyperpolarizability. It is demonstrated that the carbon nanotubes exhibit significantly larger second hyperpolarizabilities compared to a fullerene containing the same number of carbon atoms. Furthermore, the calculations show that the carbon nanotubes have a much larger directionality of the static second hyperpolarizability than the fullerenes.
ELECTROSTATIC SCREENING IN FULLERENE MOLECULES
Modern Physics Letters B, 1993
The screening properties of fullerene molecules are described by means of a continuum model which uses the electronic wavefunctions of planar graphite as a starting point. The long distance behavior of the system gives rise to a renormalizable theory, which flows towards a non trivial fixed point. Its existence implies an anomalous dielectric constant. The screening properties are neither metallic nor insulating. Alternatively, the intramolecular screening is obtained from a simple approximation to the electronic wavefunctions. Intermolecular effects are also calculated, As a consistency check, it is shown that the observed polarizability of C 60 is well eproduced. 75.10.Jm, 75.10.Lp, 75.30.Ds.
Charge–Metal Interaction of a Carbon Nanotube
Chemphyschem, 2007
While the electronic structure of metallic single-walled carbon nanotubes, SWCNTs, is well-understood, only a few, perhaps too rare, steps have been taken to investigate the metallic contribution to their interactions with charged species. This is not to say that interactions between SWCNTs and molecules have not been studied, but rather that the additional metallic contribution to the interaction with a (partial) charge has often been left unquantified or even neglected. And yet, this is not a trivial issue because prior to many of the practical applications advocated for SWCNTs there is the separation of metallic from semiconducting tubes that could be based on the larger adsorption energy of charged molecules when bound to metallic nanotubes. It was, for instance, noticed that for DNAnanotube hybrids, the negative charge of DNA induces a positive charge on the tube so that the overall charge is smaller to that of pure DNA and, although not quantified, this effect was used to separate metallic from semiconducting nanotubes. Moreover, if the additional metallic contribution is neglected, results of interactions/simulations with tubes of similar radius, such as (10,10) and (17,0), become equivalent, although the former is metallic and the latter semiconducting. Quantum chemical calculations can differentiate between the interaction of a metallic, or a semiconducting, nanotube with a charged species in a way analogous to that of Lu and co-workers who used first-principles calculations to show that the larger electronic polarizability of metallic SWCNTs makes them interact more strongly with adsorbates via p interactions. Quantum chemical calculations, however, routinely handle only a limited number of atoms and may have difficulties with weakly binding van der Waals interactions. If extensive systems of thousands of atoms must be considered and non-bonding interactions play a major role, classical potentials must be applied and they usually do not include this metallic contribution. Quantum chemical calculations, however, routinely handle only a limited number of atoms and if proper periodic boundary conditions are not implemented, that is, a cluster approach is employed, the metallic nature of the SWCNT may disappear.
The Atomic Partial Charges Arboretum: Trying to See the Forest for the Trees
ChemPhysChem, 2020
Atomic partial charges are among the most commonly used interpretive tools in quantum chemistry. Dozens of different 'population analyses' are in use, which are best seen as proxies (indirect gauges) rather than measurements of a 'general ionicity'. For the GMTKN55 benchmark of nearly 2,500 main-group molecules, which span a broad swathe of chemical space, some two dozen different charge distributions were evaluated at the PBE0 level near the 1-particle basis set limit. The correlation matrix between the different charge distributions exhibits a block structure; blocking is, broadly speaking, by charge distribution class. A principal component analysis on the entire dataset suggests that nearly all variation can be accounted for by just two 'principal components of ionicity': one has all the distributions going in sync, while the second corresponds mainly to Bader QTAIM vs. all others. A weaker third component corresponds to electrostatic charge models in opposition to the orbital-based ones. The single charge distributions that have the greatest statistical similarity to the first principal component are iterated Hirshfeld (Hirshfeld-I) and a minimal-basis projected modification of Bickelhaupt charges. If three individual variables, rather than three principal components, are to be identified that contain most of the information in the whole dataset, one representative for each of the three classes of Corminboeuf et al. is needed: one based on partitioning of the density (such as QTAIM), a second based on orbital partitioning (such as NPA), and a third based on the molecular electrostatic potential (such as HLY or CHELPG).