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Minima, one transition state, the minimum-energy path, and three tunneling paths at different temperatures found with the optimization library DL-FIND.

DL-FIND is a program library to characterize potential energy surfaces of chemical systems. Minima (stable intermediates), transition states and paths connecting them optimally can be located. These allow to simulate chemical reactions. The potential energy is calculated by external programs. For that task, quantum chemical calculations, empirical force fields, as well as their QM/MM combination are currently available.

Apart from standard minimization algorithms we focus the development on transition-state-search in systems with many degrees of freedom. The dimer method and the nudged-elastic band algorithm allow the location of transition states without expensive computations of the Hessian $ndash; in contrast to standard algorithms. Delocalized internal coordinates improve the convergence. Hybridized with Cartesian coordinates they are especially suited for large systems. Optimization of tunneling paths allows the estimation of atom tunneling rates.

DL-FIND is written in Fortran 95. It is distributed open-source under the L-GPL license. Lead by Johannes Kästner, the code is mainly developed at the University of Stuttgart and Daresbury Lab (UK).

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