Induction/dispersion interactions evaluation

For the evaluation of the averaged induction-dispersion interaction we here... 

For the evaluation of the averaged induction-dispersion interaction -Ce/ " , we here accept based on the Slater-Kirkwood formnla valne Ce=23.2 from the work [23], In order to create more reliable estimations of the anisotropy of Ce term, one can again resort to the RSOF method by Meyer et al. [6] and to the related calculations of the fragment dynamic polarizabilities [20, 30], The FFC basis of Eq.25 consists of 36 functions transforming upon time inversion as... 

It has recently become clear that classical electrostatics is much more useful in the description of intermolecular interactions than was previously thought. The key is the use of distributed multipoles, which provide a compact and accurate picture of the charge distribution but do not suffer from the convergence problems associated with the conventional one-centre multipole expansion. The article describes how the electrostatic interaction can be formulated efficiently and simply, by using the best features of both the Cartesian tensor and the spherical tensor formalisms, without the need for inconvenient transformations between molecular and space-fixed coordinate systems, and how related phenomena such as induction and dispersion interactions can be incorporated within the same framework. The formalism also provides a very simple route for the evaluation of electric fields and field gradients. The article shows how the forces and torques needed for molecular dynamics calculations can be evaluated efficiently. The formulae needed for these applications are tabulated. 

There exist several intermolecular forces between an aromatic molecule and an interacting molecule [15]. Computational methods for their evaluation will be briefly explained in this section. Dispersion, electrostatic and exchange-repulsion interactions are the major intermolecular forces when the interacting molecules are both neutral. The dispersion contribution has paramoimt importance for the attraction in the tt/tt, OH/tt, NH/tt and CH/tt interactions [8-10,16] therefore, accurate calculation of the dispersion energy is essential for the quantitative evaluation of these interactions. On the other hand, electrostatic and induction (induced polarization) interactions are the major source of the attraction in the cation/TT interaction [17]. The contribution of the dispersion interaction is relatively small in the cation/TT interactions. 

The use of LOs in the evaluation of MEP and of ES is bimolecular interaction was examined by Amos and Crispin [176] who suggested the use of localized electron distributions also for induction and dispersion contributions to AE. We have already quoted a paper by Mezei and Campbell [107] where the use of LOs is examined and compared to other partitions of the molecular charge distribution. 

A useful alternative approach is to isolate the components of the perturbation expansion, namely the repulsion, electrostatic interaction, induction, and dispersion terms, and to calculate each of them independently by the most appropriate technique. Thus the electrostatic interaction can be calculated accurately from distributed multipole descriptions of the individual molecules, while the induction and dispersion contributions may be derived from molecular polarizabilities. This approach has the advantage that the properties of the monomers have to be calculated only once, after which the interactions may be evaluated easily and efficiently at as many dimer geometries as required. The repulsion is not so amenable, but it can be fitted by suitable analytic functions much more satisfactorily than the complete potential. The result is a model of the intermolecular potential that is capable of describing properties to a high level of accuracy. 

DPT calculations are not suitable for evaluating the inter molecular interactions of aromatic molecules, as dispersion is the major source of the attraction in the interactions of aromatic molecules, with the exception of cation/TT interactions. DPT calculations using basis sets with polarization functions provide sufficiently accurate intermolecular interaction energies for the cation/TT interactions, as DPT calculations can reproduce electrostatic and induction energies sufficiently accurately. 

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