D Chemical Dynamics

It does not seem practical to use bond-centered fitting functions in chemical dynamics calculations in which bonds are being broken and reformed. Thus our fitting functions are uncontracted and scaled from the 6-311G orbital sets in the s manifold. The atomic L 0 fitting functions are unsealed and contracted exactly as optimized for Turbomole calculations [14] except that the silicon basis is uncontracted. The calculations are performed in Cs symmetry. 

The number of it and o electrons is not monitored during the dynamics, but the number of unpaired spins is. Most often the number of unpaired spins changes fractionally and thus slowly, but once a jump of six was seen for a few tens of steps with no noticeable accompanying error in the total energy. 

The ONNO-ONNO Van der Waal s distance was found by optimizing the geometry of that system. It is slightly more than 3 Angstroms. So all collisions are started with all inter-dimer atomic distances greater than 3.5 Angstroms. 

The Xa method has been made analytic and variational via single-center, LCGTO, robust, and variational fitting. It is quite promising because, unlike empirical and semiempirical methods, it is applicable to all elements. In fact, it has an independent parameter for each element that can be optimized to give 

The Office of Naval Research directly and through the Naval Research Laboratory supported this research. 

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Geissler, P.L., Dellago, C., Chandler, D. Chemical dynamics of the protonated water trimer analyzed by transition path sampling, Phys. Chem. Chem. Phys. 1999,1,1317-22. 

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