Intermolecular interactions electrostatic interaction energy

Interaction BH-BH in the linear configuration, a) Electrostatic interaction energy and the first terms of its multipole expansion, Intermolecular distance, R,and quadrupole and octupole moments refer to the centers of mass, b) SCF interaction energy and its components. 

The electrostatic interaction energies are evaluated using the multipole expansion formulas for each intermolecular pair of sites. Explicit expressions for all terms up to R are given in Ref. 117, and for terms up to R in Ref. 118. Stone has provided a general formulation and discussion of the spherical tensor and Cartesian tensor approaches. The program ORIENT incorporates... 

Consider the case of two neutral, linear, dipolar molecules, such as HCN and KCl, in a coordinate system with its origin at the CM of molecule A and the z-axis aligned with the intermolecular vector r pointing from the CM of A to the CM of B. The relative orientation of the two molecules is uniquely specified by their spherical polar angles and the difference < ) = < )a- I>b between their azimuthal angles. The leading term in the multipole expansion of the electrostatic interaction energy is the dipole-dipole term... 

The non-covalent forces have a quantum mechanical basis, but much of their nature can be understood using a classical or semi-classical picture. Studies of intermolecu-lar interactions in the gas phase [1] suggest that the intermolecular (non-covalent) interaction energy between two molecules can be broken down into 5 main components (1) electrostatic, (2) exchange repulsion, (3) dispersion, (4) polarization and (5) charge transfer. 

The electrostatic interaction energy of two molecules can be calculated from formula (13.5). However, it is very important for a chemist to be able to predict the main features of the electrostatic interaction without any calculation at all, based on some general rules. This will create chemical intuition or chemical common sense so important in planning, performing and understanding raperiments. The data of Table 13.2 were obtained assuming a long intermolecular distance and the molecular orientations as shown in the table. 

Then, the first-order correction to the energy represents what is called the electrostatic interaction energy. E = Eelst = (l A,oV fi,ol l A,oV 5,o)> which is the Coulombic interaction (at a given intermolecular distance) of the frozen charge density distributions of the individual, non-interacting molecules. After using the multipole expansion, E i can be divided into the sum of the multipole-multipole interactions plus a remainder, called the penetration energy. A multipole-multipole interaction corresponds to the permanent multipoles of the isolated molecules. An individual multipole-multipole interaction term (2 —pole with 2 —pole) vanishes asymptotically as e.g., the dipole-dipole term decreases as = R. ... 

Koritsanszky, T. S. Coppens, P. Chemical applications of X-ray charge-density analysis, Chem. Revs. 2001, 101, 1583-1627 Volkov, A. Coppens, P. Calculation of electrostatic interaction energies in molecular dimers from atomic multipole moments obtained by different methods of electron density partitioning, J. Comp. Chem. 2004, 25, 921-934 Suponitsky, K. Y Tsirelson, V. G. Fell, D. Electron-density-based calculations of intermolecular energy the case of urea, Acta Cryst. 1999, A55, 821-827. 

In a solution of a solute in a solvent there can exist noncovalent intermolecular interactions of solvent-solvent, solvent-solute, and solute—solute pairs. The noncovalent attractive forces are of three types, namely, electrostatic, induction, and dispersion forces. We speak of forces, but physical theories make use of intermolecular energies. Let V(r) be the potential energy of interaction of two particles and F(r) be the force of interaction, where r is the interparticle distance of separation. Then these quantities are related by... 

The link between UpophiUcity and point charges is given by intermolecular electrostatic interactions (Sections 12.1.1.2, 12.1.3 and 12.1.4 address this topic) and ionization constants. The mathematical relationships between Upophilicity descriptors and pKjS are discussed in detail in Chapter 3 by Alex Avdeef. Here, we recall how pKj values are related to the molecular electron flow by taking the difference between the pfCj of aromatic and aUphatic amines as an example. The pfCa of a basic compound depends on the equilibrium shown in Fig. 12.2(A). A chemical effect produces the stabilization or destabiUzation of one of the two forms, the free energy difference (AG) decreases or increases and, consequently. 

Piquemal J-P, Gresh N, Giessner-Prettre C (2003) Improved formulas for the calculation of the electrostatic contribution to intermolecular interaction energy from multipolar expansion of the electronic distribution. J Phys Chem A 107 10353... 

Gresh N, Piquemal J-P, Krauss M (2005) Representation of Zn(II) complexes in polarizable molecular mechanics. Further refinements of the electrostatic and short-range contribution of the intermolecular interaction energy. Comparisons with parallel ab initio computations. J Comput Chem 26 1113... 

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