Dynamic polarizability model

Lamoureux G, Harder E, Vorobyov IV, Roux B, MacKerell AD (2006) A polarizable model of water for molecular dynamics simulations of biomolecules. Chem Phys Lett 418(l-3) 245-249... 

Yu HB, Geerke DP, Liu HY, van Gunsteren WE (2006) Molecular dynamics simulations of liquid methanol and methanol-water mixtures with polarizable models. J Comput Chem 27(13) 1494-1504... 

Lu ZY, Zhang YK (2008) Interfacing ab initio quantum mechanical method with classical Drude os-illator polarizable model for molecular dynamics simulation of chemical reactions. J Chem Theory Comput 4(8) 1237-1248... 

Polarized Raman spectra from the alkali fluorides LiF, NaF and CsF habe been observed with argon laser excitations by Evans and Fitchen 09). These spectra are of interest as an extreme test of lattice dynamics theories and polarizability models. 

In contrast to the just discussed classical models [43,44], authors of works [38, 39] treated the problem of the dynamical polarizability ay(carbon cage quantum-mechanically, utilizing the 5-potential model concept, where the C60 cage is simulated by the Dirac 5-potential, V(r) = —Vo8(Rc—r). However, instead of calculating cy( >) directly, the latter was determined from experimental data on the C60 photoabsorption cross section a (o>) [60, 61] with the help of the dispersion relations for the real Re ay and imaginary Imay parts of the dipole polarizability ay ( >) ... 

Korona T, Przybytek M, Jeziorski B. Time-independent coupled cluster theory of the polarization propagator. Implementation and application of the singles and doubles model to dynamic polarizabilities and Van der Waals constants, 2006. Submitted to Mol. Phys 104 2302-2316... 

Recent sequential molecular dynamics/quantum mechanics (MD/QM) calculations of the water dipole moment [51] using a polarizable model for water [52] indicate that the average dipole moment in the liquid is not dependent on the number... 

The polarizable point dipole model has also been used in Monte Carlo simulations with single particle moves.When using the iterative method, a whole new set of dipoles must be computed after each molecule is moved. These updates can be made more efficient by storing the distances between all the particles, since most of them are unchanged, but this requires a lot of memory. The many-body nature of polarization makes it more amenable to molecular dynamics techniques, in which all particles move at once, compared to Monte Carlo methods where typically only one particle moves at a time. For nonpolarizable, pairwise-additive models, MC methods can be efficient because only the interactions involving the moved particle need to be recalculated [while the other (N - 1) x (]V - 1) interactions are unchanged]. For polarizable models, all N x N interactions are, in principle, altered when one particle moves. Consequently, exact polarizable MC calculations can be... 

In the liquid phase, calculations of the pair correlation functions, dielectric constant, and diffusion constant have generated the most attention. There exist nonpolarizable and polarizable models that can reproduce each quantity individually it is considerably more difficult to reproduce all quantities (together with the pressure and energy) simultaneously. In general, polarizable models have no distinct advantage in reproducing the structural and energetic properties of liquid water, but they allow for better treatment of dynamic properties. 

In spite of the practical usefulness of such empirical sector mles, the physical origin of the optical activity in these molecules remains an open question. In fact, polarizability calculations (both by means of the Weigang amplified sector mle for allowed transitions and the DeVoe dynamic coupling model), taking full account of the interaction between the Ag — transition dipole and the polarizable matter around it, give the wrong sign. 

Veldhuizen and de Leeuw (1996) used the OPLS parameters for methanol and both a nonpolarizable and a polarizable model for carbon tetrachloride for MD simulations over a wide range of compositions. The polarization contribution was found to be very important for the proper description of mixture properties, such as the heat of mixing. A recent study by Gonzalez et at (1999) of ethanol with MD simulations using the OPLS potential concluded that a nonpolarizable model for ethanol is sufficient to describe most static and dynamic properties of liquid ethanol. They also suggested that polarizabilities be introduced as atomic properties instead of the commonly approach of using a single molecular polarizability. 

The molecular dynamics simulation is performed using the MOTECC suite of programs (Sciortino, Corongiu and dementi, 1994) in the context of microcanonical statistical ensemble. The system considered is a cube with periodic boundary conditions, which contains 343 water molecules. Compatibility of this data with the water experimental density of0.998 g/cm requires a cube with a side length of 21.7446 A. In accordance with the polarizable model, a spherical cutoff with radium equal to half of the simulation cube side is imposed, together with a switching function to suppress energy drift. 

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