Studying chemical reactivity in a virtual environment

Abstract

Chemical reactivity of a set of reactants is determined by its potential (electronic) energy (hyper)surface. The high dimensionality of this surface renders it difficult to efficiently explore reactivity in a large reactive system. Exhaustive sampling techniques and search algorithms are not straightforward to employ as it is not clear which explored path will eventually produce the minimum energy path of a reaction passing through a transition structure. Here, the chemist's intuition would be of invaluable help, but it cannot be easily exploited because (1) no intuitive and direct tool for the scientist to manipulate molecular structures is currently available and because (2) quantum chemical calculations are inherently expensive in terms of computational effort. In this work, we elaborate on how the chemist can be reintroduced into the exploratory process within a virtual environment that provides immediate feedback and intuitive tools to manipulate a reactive system. We work out in detail how this immersion should take place. We provide an analysis of modern semi-empirical methods which already today are candidates for the interactive study of chemical reactivity. Implications of manual structure manipulations for their physical meaning and chemical relevance are carefully analysed in order to provide sound theoretical foundations for the interpretation of the interactive reactivity exploration.

Interactive Chemical Reactivity Exploration

“…Moreover, the DFTB energy profiles exhibits too small dissociation energies. This is not a major drawback as the haptic exploration of the molecular system requires only a qualitatively correct potential energy surface [12]. Figure 4 also shows that the ASED-MO method with the chosen parameters overestimates equilibrium bond lengths.…”

“…It has to be a strictly positive function of the input force f in and is not allowed to have any zero crossings (apart from the one at the origin), since they would introduce artificial extremal points on the surface [12]. The scaling function chosen for our implementation takes care of the necessary unit conversion and the adaptation of the force range to the range of the haptic device.…”

“…Haptic Quantum Chemistry [7,8], Interactive Quantum Chemistry [9,10] and Real-time Quantum Chemistry [11,12] offer new alternative approaches to study reactivity in large three-dimensional molecular systems by providing an instantaneous response of the system to the structural manipulation.…”

Real-time feedback from iterative electronic structure calculations

“…To assess the reliability of surrogate potentials for real‐time feedback, the real‐time exploration of a hydride shift reaction with variable side chain length, shown in Figure , was studied with and without surrogate potentials.…”

“…It allows designing new reactions and optimizing existing ones. In recent years, approaches toward interactive reactivity studies have been introduced.…”