Research Area C
Publications 2013

We present a linear-scaling symmetry-adapted perturbation theory (SAPT) method that is based on an atomic orbital (AO) formulation of zeroth-order SAPT (SAPT0). The non-dispersive terms are realized with linear-scaling cost using both the continuous fast multipole method (CFMM) and the linear exchange (LinK) approach for integral ... READ MORE

The 1H NMR chemical shifts of the C(α)H protons of arylmethyl triphenylphosphonium ions in CD2Cl2 solution strongly depend on the counteranions X. The values for the benzhydryl derivatives Ph2CHPPh3+ X, for example, range from δH=8.25 ... READ MORE

The direct manipulation of charge oscillations has emerged as a new perspective in chemical reaction control. Here, we demonstrate, in a joint experimental and theoretical study, that the electron dynamics of a molecule is efficiently steered by controlling the interplay of a driving femtosecond laser pulse with the photoinduced charge oscillation. These oscillations ... READ MORE

Photolytic bond cleavage is a well-established method to generate carbocations for organic synthesis. Changes in the leaving group have a large influence on the chemical yield. The underlying potential energy surfaces governing the initial process are mostly unknown. We provide potential energy surfaces of ground and excited states on the CASSCF/CASPT2 level of ... READ MORE

Significant differences in the reactivity of norbornene derivatives in the inverse electron-demand Diels–Alder reaction with tetrazines were revealed by kinetic studies. Substantial rate enhancement for the exo norbornene isomers was observed. Quantum-chemical calculations were used to rationalize and support the observed experimental data. ... READ MORE

Three new cytosine derived DNA modifications, 5-hydroxymethyl-2′-deoxycytidine (hmdC), 5-formyl-2′-deoxycytidine (fdC) and 5-carboxy-2′-deoxycytidine (cadC) were recently discovered in mammalian DNA, particularly in stem cell DNA. Their function is currently not clear, but it is assumed that in stem cells they might be intermediates of an active demethylation ... READ MORE

Here we suggest a mixed computational and empirical approach serving to optimize the parameters of complex and polarizable molecular mechanics (PMM) models for complicated liquids. The computational part of the parameter optimization relies on hybrid calculations combining density functional theory (DFT) for a solute molecule with a PMM treatment of its solvent ... READ MORE

Hybrid molecular dynamics (MD) simulations, in which the forces acting on the atoms are calculated by grid-based density functional theory (DFT) for a solute molecule and by a polarizable molecular mechanics (PMM) force field for a large solvent environment composed of several 103–105 molecules, pose a challenge. A corresponding computational approach should ... READ MORE

Bond cleavage and bond formation are central to organic chemistry. Carbocations play a key role in our understanding of nucleophilic substitution reactions that involve both processes. The precise understanding of the mechanism and dynamics of the photogeneration of carbocations and carbon radicals is therefore an important quest. In particular, the role of electron ... READ MORE

An atomic-orbital (AO) based formulation for calculating nuclear magnetic resonance chemical shieldings at the second-order Møller-Plesset perturbation theory level is introduced, which provides a basis for reducing the scaling of the computational effort with the molecular size from the fifth power to linear and for a specific nucleus ... READ MORE

We present a simple but accurate preselection method based on Schwarz integral estimates to determine the significant elements of the exact exchange matrix before its evaluation, thus providing an asymptotical linear-scaling behavior for non-metallic systems. Our screening procedure proves to be highly suitable for exchange matrix ... READ MORE

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