Polarizable potential

Finally we mention the very recent development of a scale of directional substituent polarizability parameters from ab initio calculations of polarizability potentials . It is expected that this scale of values will prove of considerable utility in correlation analysis, often in association with Op values. The a, value of S02Me is given as — 0.62 cf. H, 0.00 NO2, - 0.26 COMe, - 0.55 SMe, - 0.68 t-Bu, - 0.75. 

Ding YB, Bernardo DN, Kroghjespersen K, Levy RM (1995) Solvation free-energies of small amides and amines from molecular-dynamics free-energy perturbation simulations using pairwise additive and many-body polarizable potentials. J Phys Chem 99(29) 11575—11583... 

Jedlovszky P, Vallauri R (1999) Temperature dependence of thermodynamic properties of a polarizable potential model of water. Mol Phys 97(11) 1157-1163... 

Bernardo DN, Ding YB, Kroghjespersen K, Levy RM (1995) Evaluating polarizable potentials on distributed-memory parallel computers - program-development and applications. J Comput Chem 16(9) 1141-1152... 

Meng, E. C. Caldwell, J. W. Kollman, P. A., Investigating the anomalous solvation free energies of amines with a polarizable potential, J. Phys. Chem. 1996,100, 2367-2371. 

This question was addressed by use of classical trajectory techniques with an ion-quadrupole plus anisotropic polarizability potential to determine the collision rate constant (k ). Over one million trajectories with initial conditions covering a range of translational temperature, neutral rotor state, and isotopic composition were calculated. The results for the thermally average 300 K values for are listed in the last column of Table 3 and indicate that reaction (11) for H2/H2, D2/D2, and HD /HD proceeds at essentially the classical collision rate, whereas the reported experimental rates for H2/D2 and D2/H2 reactions seem to be in error as they are significantly larger than k. This conclusion raises two questions (1) If the symmetry restrictions outlined in Table 2 apply, how are they essentially completely overcome at 300 K (2) Do conditions exist where the restriction would give rise to observable kinetic effects ... 

As implied, no real electrode is exactly like a polarizable or a nonpolarizable electrode. But the idealizations of completely polarizable (potential changes, but no current flows across the interphase), or completely nonpolarizable (current passes, but there is no potential change) electrodes are useful. Real electrodes tend to be more like the one or the other of the two ideals. 

In the following electronic calculations, the solute (and potentially a number of the closest water molecules) is treated using DFI7B3LYP while the rest of the solvent is treated either using the same polarizable potential as in the MD simulations (DPM) or introducing an external continuum (PCM). Acronyms like DFT(X)/DPM or DFT(X)/PCM are used here to indicate calculations where X water molecules have been included into the part of the system treated using DFT. The final molecular property in solution is evaluated as a statistical average over all these molecular clusters. 

Table 13-2. Vertical electronic n —> 7T transition energy of acetone in gas phase, Egas, and aqueous solution, Ewat, in units of eV. Excitation energy in aqueous solution was obtained from the combined QM/MM calculations treating acetone molecule at the quantum mechanical level of theory as indicated in the first column and using the polarizable potential for water molecules as a statistical average over 1200 molecular configurations extracted from classical MD simulation. The solvent shift in excitation energy, AE (in cm-1), is evaluated as a difference between excitation energies in water and in vacuum...

Carlo computer simulations, and reviews some of the systems that have been simulated with polarizable potentials. 

Water is the most common substance to be studied with polarizable potentials. An extremely large number of polarizable potentials for liquid... 

Solvation Free Energies of Small Amides and Amines from Molecular Dynamics/Free Energy Perturbation Simulations Using Pairwise Additive and Many-Body Polarizable Potentials. 

Model for Liquid Water and the Reproduction of the Density Anomaly by Rigid, Non-polarizable Potential Functions. 

For small clusters containing up to six water molecules, the OPLS [197] library of potentials leads to results of bond energy in agreement with that calculated with the polarizable potential of Caldwell et al [94]. 

Small effects of non-additive polarizability terms, included in the ion-w or w-w potentials, have been observed by Smith and Dang [118] on ion-ion pmf. In fact, the SPC/E potential combined with a simple model for the ion-water interactions (Coulomb-f-LJ) is able to reproduce the pmf obtained with the polarizable potential, within statistical uncertainty of the simulation. Also, orientational effects on water molecules of the first hydration shell are described much the same way by the two types of potential, with minor differences as to the population of bridging water, more pronounced for Cl. ... 

Recently, there were many attempts of MD simulations for the vibrational dynamics of ice. In these calculations more realistic, either non-rigid or polarizable, potentials were used. One such calculation was made by Itoh et al [72] using the KKY potential [9] which has three separate pair-wise terms yoo(r), VoH(r), VnH(r) and an extra three-body term for H-O-H and H-0—H bending. These calculations produced the all the fundamental modes up to 450 meV (or 3622 cm" ). The resulting spectra show very similar features to results from the MCY and TIP4P potentials in the translational and librational regions (see Fig. 16 and 17). 

T. M. Chang and L. X. Dang, Molecular dynamics simulations of CCI4-H2O liquid-liquid interface with polarizable potential models, J. Chem. Phys. 104 (1996) 6772. 

Dimethyl sulfoxide (DMSO) (polarizable potential) Kurinkova 1998 Dimethyl sulfoxide (DMSO)... 

Hehre, W. J., Pau, C. F., Headley, A. D., et al. (1986) A scale of directional substituent polarizability parameters from abinitio calculations of polarizability potentials. Journal of the American Chemical Society, 108(7), 1711-1712. 

The more recent ASP potentials of MUlot et al. [183] and their counterparts fitted to the experimental dimer spectra, VRT(ASP-W) [52] and VRT(ASP-W)III [53], have been utihzed in diffusion Monte Carlo (DMC) simulation of water clusters of different sizes [192,193]. The three- and higher body effects were described by a polarization model only, similarly as in empirical polarizable potentials. While polarization models are quite efficient in describing the nonadditive induction in the asymptotic regime, they fail to properly model the short-range nonadditivities, which are definitely non-negligible in smaller trimers. 

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