TSH method

It is getting more and more important to treat realistic large chemical and even biological systems theoretically by taking into account the quantum mechanical effects, such as nonadiabatic transition, tunneling, and intereference. The simplest method to treat nonadiabatic dynamics is the TSH method introduced... 

The advantages of this generalized TSH method can be summarized as follows (1) both types of transitions in the potential curve crossing problems. 

Recently, Garth Jones (UNSW) and his co-workers have described a semi-classical molecular dynamics (MD) model, which incorporates the trajectory surface hopping (TSH) method, that shows promise in investigating a number of important problems concerning the effects of molecular vibrations on the dynamics of ET reactions, including formally symmetry-forbidden ones. Essentially,... 

Thus, molecular vibrations play a crucial role in ET processes, and MD calculations involving quantum transitions, such as our MD-TSH method, offer considerable promise as a powerful tool for investigating their role in ET reactions. 

In the TSH method, the molecule always feels the potential energy surface of only one of the two adiabatic states. (For a comparison of TSH with quantum wavepackets see, e.g.. Worth et al. .) The populations a(t) are monitored to decide which adiabatic state shornd be used to compute the gradient and to propagate the nuclei. When the occupation number of a state reaches a given threshold (e.g.,... 

In those cases where the dynamics cannot be adequately described by motion on a single adiabatic potential-energy surface, additional dynamical assumptions must be made. The pioneering technique is the trajectory surface hopping (TSH) method (55,56) of Tully and co-workers. In these calculations, the classical trajectories are integrated on an adiabatic potential energy surface (typically generated by diatomics in molecules, DIM... 

In the energy region beyond 2.5 eV j absolute cross sections for the reactions (16a,b,c) have been calculated using the trajectory surface hopping (TSH) method (16a) can (but need not) proceed only on the lowest adiabatic... 

In this context, one of the most efficient approaches is based on mixed quantum-classical dynamics in which the nonadiabatic effects are simulated using Tully s surface hopping (TSH) method [13, 14]. It is applicable to a large variety of systems ranging from isolated molecules and clusters to complex nanostructures... 

In this section we briefly outline our formulation of the nonadiabatic dynamics in the framework of TDDFT using localized Gaussian basis sets combined with Tully s surface hopping (TSH) method [13]. Within the TSH procedure, nonadiabatic... 

Recently, Hoffmann and Schatz(7ij have developed a new level of treatment of spin-orbit effects in bimolecular reactions which enables a more sophisticated treatment of intersystem crossing d3mamics than in the past. In this treatment high quality electronic structure n thods are used to determine global surfaces for the reaction and spin-orbit matrix elements, and then trajectory surface hopping (TSH) methods are used to determine properties of the bimolecular collisions such as reactive cross sections and state distribution information. In an application of this theory to the O + H2 reaction, the spin-orbit matrix elements were determined as a function of position, and then TSH calculations were done within a diabatic representation to determine cross sections. Intersystem crossing effects were found to be small for O + H2 due to... 

Additional results of this study were concerned with the use of TSH methods to describe intersystem crossing dynamics. We find that the TSH-D method is capable of determining reaction probabilities of reasonable accuracy for two models (1 and 7) where intersystem crossing is dominant, but TSH-A seriously overestimates these probabilities. This conclusion supports tiie interpretation of HS, who used TSH-D in preference to TSH-A in their full dimensionality calculations on O + H2. 

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