Asmus O Dohn

Technical University of Denmark (DTU), DTU Chemistry, Post-Doc

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Femtosecond structural dynamics of spin-crossover compounds and the energy flow from excited state species to the solvent

by Tobias C B Harlang and Asmus O Dohn

Optimizing the Structure of Tetracyanoplatinate (II): A Comparison of Relativistic Density Functional Theory Methods

by Asmus O Dohn and Stephan P. A. Sauer

The geometry of tetracyanoplatinate(II) (TCP) has been optimized with density functional theory (... more The geometry of tetracyanoplatinate(II) (TCP) has been optimized with density functional theory (DFT) calculations in order to compare different computational strategies. Two approximate scalar relativistic methods, i.e. the scalar zeroth-order regular approximation (ZORA) and non-relativistic calculations with relativistic effective core potentials (ECPs), were benchmarked against the four-component fully relativistic approach using the Dirac-Coulomb Hamiltonian and all-electron non-relativistic calculations. We find that the 5% contraction of the platinum-carbon bond due to relativistic effects is almost quantitatively reproduced in the ZORA and ECP calculations. In addition, the effect of the exchange-correlation functional and one-electron basis set was studied by employing the two generalized gradient approximation (GGA) functionals, BLYP and PBE, as well as their hybrid version B3LYP and PBE0 in combination with both correlation consistent and Ahlrichs type basis sets. The platinum-carbon bond length (relativistic or non-relativistic) is approximately 1% shorter on using the PBE exchange-correlation functional compared to the BLYP functional but including exact exchange has no significant effect. For the C-N bond these trends are reversed and an order of magnitude smaller. With respect to the basis set dependence we observed that a triple zeta basis set with polarization functions gives in general sufficiently converged results, but while for the Pt-C bond it is advantageous to include extra diffuse functions, this did not turn out to be important for the C-N bond.

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On the calculation of x-ray scattering signals from pairwise radial distribution functions

We derive a formulation for evaluating (time-resolved) x-ray scattering signals of solvated chemi... more We derive a formulation for evaluating (time-resolved) x-ray scattering signals of solvated
chemical systems, based on pairwise radial distribution functions, with the aim of this
formulation to accompany molecular dynamics simulations. The derivation is described in detail
to eliminate any possible ambiguities, and the result includes a modification to the atom-type
formulation which to our knowledge is previously unaccounted for. The formulation is
numerically implemented and validated.

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Bond Shortening (1.4 angstrom) in the Singlet and Triplet Excited States of [Ir-2(dimen)(4)](2+) in Solution Determined by Time-Resolved X-ray Scattering

by Tobias C B Harlang, Niels Harrit, and Asmus O Dohn

Inorganic Chemistry, 2011

Direct Dynamics Studies of a Binuclear Metal Complex in Solution: The Interplay Between Vibrational Relaxation, Coherence, and Solvent Effects

by Niels Henriksen and Asmus O Dohn

The Journal of Physical Chemistry Letters, 2014

ABSTRACT By using a newly implemented QM/MM multiscale MD method to simulate the excited state dy... more ABSTRACT By using a newly implemented QM/MM multiscale MD method to simulate the excited state dynamics of the Ir 2 (dimen) 4 2+ (dimen = 1,8-diisocyano-p-menthane) complex, we not only report on results that support the two experimentally observed coherent dynamical modes in the molecule but also reveal a third mode, not distinguishable by spectroscopic methods. We directly follow the channels of energy dissipation to the solvent and report that the main cause for coherence decay is the initial wide range of configurations in the excited state population. We observe that the solvent can actually extend the coherence lifetime by blocking channels for intramolecular vibrational energy redistribution (IVR).

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