Intermolecular energy potential

Jeziorski B, Moszynski R and Szalewicz K 1994 Perturbation theory approach to intermolecular potential energy surfaces of van der Waals complexes Chem. Rev. 94 1887... 

These results shown in Figures 1 and 2 demonstrate the similarity of the effects of short-range forces on the properties of nonelectrolytes and concentrated electrolytes. One finds both positive and negative deviations from ideality and these effects may be ascribed to the difference between the intermolecular potential energy of attraction of unlike species to the mean of the corresponding potentials for pairs of like molecules. Previous discussion of these systems has focused on the hydration of the positive ion as the dominant effect, but we see in Figure 1 that... 

Now consider the energy of interaction of an isolated pair as the center to center distance, R, changes. In the transfer from dilute to non-ideal gas (dimer), or to the condensed phase, important changes occur in all degrees of freedom. This is diagramed in Fig. 5.1 which shows the shifts in intermolecular potential energy... 

Precise intermolecular potentials are available for monatomic He, Ne, Ar and Xe. This permits accurate calculations of the VPIE s of these gases, their mixtures, and rare gas isotopomer mixtures. To begin, we are reminded that the mean intermolecular potential energy, , and mean force constant < V2U> can be obtained from the pair correlation function of the fluid, g(r),... 

Tbe results for water are mainly available from computer simulations, although some results of integral equation theories have been reported in recent years. Despite the varied nature of the intermolecular potential energy functions used, most of these studies give a qualitatively similar picture. As an example, we consida in some detail the results obtained for the potential energy function given above (for the interface between water and Pt). 

In principle, it is a simple matter to include solvent water molecules directly in MD simulations, since appropriate intermolecular potential energy functions for water are available (1Z 37,38) one would just surround the solute molecules with a sufficient number of water molecules to approximate a bulk solution. Unfortunately, a "sufficient number of water molecules might be enormous, since many of the effects of aqueous solvation are long range or are due to entropic contributions arising from "structuring of the solvent, which may be cooperative in nature. 

For non-polar molecules, a commonly used "intermolecular potential energy factor is the Lennard-Jones (6-12) Potential ... 

For polar molecules, the most widely used intermolecular potential energy is the Stockmayer Potential ... 

It is customary to split the intermolecular potential energy function p(r) into two parts ... 

Spherical nonpolar molecules obey an interaction potential which has the characteristic shape shown in Fig. 2. At large values of the separation r it is known that the potential curve has the shape — r 6, and at short distances the potential curve rises exponentially the exact shape of the bottom part of the curve is not very well known. Numerous empirical equations of the form of Eq. (78) have been suggested for describing the molecular interaction given pictorially in Fig. 2. The discussion here is restricted to the two most important empirical functions. A rather complete summary of the contributions to intermolecular potential energy and empirical intermolecular potential energy functions used in applied statistical mechanics may be found in (Hll, Sec. 1.3) ... 

Fig. 2. Sketch showing general form of the intermolecular potential energy function.

Short Table of Intermolecular Potential-Energy Parameters... 

Intermolecular potential energy of interaction A Mass flux of A with respect to molar-average velocity (see Table III) I a Molar flux of A with respect to molar-average velocity (see Table III) (38)... 

The driving force for diffusion is the thermal energy, fcB T, associated with Brownian motion. By contrast, for reactions between ions of charges zAe and zBe, the direct intermolecular potential energy becomes very important and is the Coulomb interaction... 

Finally, the reduced collision integral is usually expressed in terms of a reduced temperature T. If the intermolecular potential energy function can be expressed in the form [178]... 

Figure 11.3 Variations of the intermolecular potential energy u(d) with inter-molecular distance d d0 is the equilibrium distance at which u(d) = -CED (CED = cohesive energy density) dw is the van der Waals distance at which V = Vw and dg is the abscissa of the inflection point and corresponds to the glass transition.

Nesbitt, D.J., Child, M.S., and Clary, D.C. (1989). Rydberg-Klein-Rees inversion of high resolution van der Waals infrared spectra An intermolecular potential energy surface for Ar+HF(t = 1), J. Chem. Phys. 90, 4855-4864. 

Leland and Co-workers (8-10) have been able to re-derive the van der Waals mixing rules with the use of statistical mechanical theory of radial distribution functions. According to these investigators, for a fluid mixture with a pair intermolecular potential energy function,... 

If MM is chosen as the low level method in ONIOM, the approach falls into the general class of the QM/MM strategies (see refs [21,22] and references cited therein). However, in most of the QM/MM approaches, one calculation is run a QM method is applied to the core of the system and the rest (usually the largest part) is treated by a force field that contains intramolecular and intermolecular potential energy terms in the form of analytic functions. The interaction of the MM environment with the QM chromophore is represented by the hamiltonian term. 7/yM/MM will include the... 

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