Direct molecular dynamics reaction

Asymptotic analysis, electronic states, triatomic quantum reaction dynamics, 317—318 Azulene molecule, direct molecular dynamics, complete active space self-consistent field (CASSCF) technique, 408-410... 

Infinite-order sudden approximation (IOSA), electron nuclear dynamics (END), molecular systems, 345-349 Initial relaxation direction (IRD), direct molecular dynamics, theoretical background, 359-361 Inorganic compounds, loop construction, photochemical reactions, 481-482 In-phase states ... 

As discussed by M. Shapiro and R Brumer in the book Quantum Control of Molecular Processes, there are two general control strategies that can be applied to harness and direct molecular dynamics optimal control and coherent control. The optimal control schemes aim to find a sef of external field parameters that conspire - through quantum interferences or by incoherent addition - to yield the best possible outcome for a specific, desired evolution of a quantum system. Coherent control relies on interferences, constructive or destructive, that prohibit or enhance certain reaction pathways. Both of these control strategies meet with challenges when applied to molecular collisions. 

Ab Initio Direct Molecular Dynamics Studies of Atmospheric Reactions Interconversion of Nitronium Ions and Nitric Acid in Small Clusters (Y. Ishikawa R. C. Binning, Jr.)... 

Yasuyuki Ishikawa, Juan J. Mateo, Donald A. Tryk, Carlos R. Cabrera Direct molecular dynamics and density-functional theoretical study of the electrochemical hydrogen oxidation reaction and underpotential deposition of H on Pt(l 11), "Journal of Electro-analytical Chemistry", 607, 37-46 (2007). 

The above description is formal and although the rate calculation is well-posed it is difficult to carry out for problems of chemical interest. Hence, much of the focus of recent theoretical studies of reaction rates in the condensed phases has centered on evaluation of the reaction rate for model systems [8]. Perhaps the best way to obtain information on the structure of the rate coefficient expressions is through direct molecular dynamics simulations on model systems. Since both of these approaches have been reviewed by others in this volume, we now turn our attention to far-from-equilibrium systems where some of the ideas summarized above can be used, but new phenomena appear which require special techniques. 

The direct dissociation of diatomic molecules is the most well studied process in gas-surface dynamics, the one for which the combination of surface science and molecular beam teclmiques allied to the computation of total energies and detailed and painstaking solution of the molecular dynamics has been most successful. The result is a substantial body of knowledge concerning the importance of the various degrees of freedom (e.g. molecular rotation) to the reaction dynamics, the details of which are contained in a number of review articles [2, 36, 37, 38, 39, 40 and 41]. 

Election nuclear dynamics theory is a direct nonadiababc dynamics approach to molecular processes and uses an electi onic basis of atomic orbitals attached to dynamical centers, whose positions and momenta are dynamical variables. Although computationally intensive, this approach is general and has a systematic hierarchy of approximations when applied in an ab initio fashion. It can also be applied with semiempirical treatment of electronic degrees of freedom [4]. It is important to recognize that the reactants in this approach are not forced to follow a certain reaction path but for a given set of initial conditions the entire system evolves in time in a completely dynamical manner dictated by the inteiparbcle interactions. 

Once a PES has been computed, it is often fitted to an analytic function. This is done because there are many ways to analyze analytic functions that require much less computation time than working directly with ah initio calculations. For example, the reaction can be modeled as a molecular dynamics simulation showing the vibrational motion and reaction trajectories as described in Chapter 19. Another technique is to fit ah initio results to a semiempirical model designed for the purpose of describing PES s. 

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