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Marsalek O.,Czech Institute of Organic Chemistry And Biochemistry | Marsalek O.,Academy of Sciences of the Czech Republic | Uhlig F.,Wilhelm Ostwald Institute For Physikalische Und Theoretische Chemie | Jungwirth P.,Czech Institute of Organic Chemistry And Biochemistry | Jungwirth P.,Academy of Sciences of the Czech Republic
Journal of Physical Chemistry C | Year: 2010

Ab initio molecular dynamics simulations were performed with the aim to follow two scenarios for an excess electron in cold water clusters. In the first one, an electron is attached to a quenched neutral cluster. Such an electron, initially very delocalized and loosely bound, shrinks somewhat and increases its vertical detachment energy to 1 - 1.5 eV within several picoseconds. Unlike in warm liquid clusters, the electron in this cold system does not, however, reach a more compact and strongly bound structure. In contrast, if an equilibrated negatively charged water cluster with a well-localized excess electron is instantaneously quenched to ∼0 K, the electron remains strongly bound in a water cavity and practically does not change its size and binding energy. These results have important consequences for detailed interpretation of photoelectron spectroscopy measurements of electrons solvated in aqueous clusters and liquid water microjets. © 2010 American Chemical Society. Source

Marsalek O.,Czech Institute of Organic Chemistry And Biochemistry | Uhlig F.,Wilhelm Ostwald Institute For Physikalische Und Theoretische Chemie | Frigato T.,Free University of Berlin | Schmidt B.,Free University of Berlin | Jungwirth P.,Czech Institute of Organic Chemistry And Biochemistry
Physical Review Letters | Year: 2010

The process of electron localization on a cluster of 32 water molecules at 20, 50, and 300 K is unraveled using ab initio molecular dynamics simulations. In warm, liquid clusters, the excess electron relaxes from an initial diffuse and weakly bound structure to an equilibrated, strongly bound species within 1.5 ps. In contrast, in cold, glassy clusters the relaxation processes is not completed and the electron becomes trapped in a metastable surface state with an intermediate binding energy. These results question the validity of extrapolations of the properties of solvated electrons from cold clusters of increasing size to the liquid bulk. © 2010 The American Physical Society. Source

Ruger R.,Scientific Computing and Modelling NV | Ruger R.,VU University Amsterdam | Ruger R.,Wilhelm Ostwald Institute For Physikalische Und Theoretische Chemie | Van Lenthe E.,Scientific Computing and Modelling NV | And 2 more authors.
Journal of Chemical Physics | Year: 2016

We propose a new method of calculating electronically excited states that combines a density functional theory based ground state calculation with a linear response treatment that employs approximations used in the time-dependent density functional based tight binding (TD-DFTB) approach. The new method termed time-dependent density functional theory TD-DFT+TB does not rely on the DFTB parametrization and is therefore applicable to systems involving all combinations of elements. We show that the new method yields UV/Vis absorption spectra that are in excellent agreement with computationally much more expensive TD-DFT calculations. Errors in vertical excitation energies are reduced by a factor of two compared to TD-DFTB. © 2016 Author(s). Source

Cremer T.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kolbeck C.,Friedrich - Alexander - University, Erlangen - Nuremberg | Lovelock K.R.J.,University of Nottingham | Paape N.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 8 more authors.
Chemistry - A European Journal | Year: 2010

Ten [C8C1Im]+ (1-methyl-3- octylimidazolium)-based ionic liquids with anions Cl-, Br -, I-, [NO3]-, [BF4] -, [TfO]-, [PF6]-, [Tf 2N]-, [Pf2N]-, and [FAP]- (TfO = trifluoromethylsulfonate, Tf2N = bis(trifluoromethylsulfonyl) imide, Pf2N = bis(pentafluoroethylsulfonyl)imide, FAP = tris-(pentafluoroethyl)trifluorophosphate) and two [C8C 1C1Im]+ (1,2-dimethyl-3-octylimidazolium)-based ionic liquids with anions Br- and [Tf2N]- were investigated by using X-ray photoelectron spectroscopy (XPS), NMR spectroscopy and theoretical calculations. While1H NMR spectroscopy is found to probe very specifically the strongest hydrogen-bond interaction between the hydrogen attached to the C2 position and the anion, a comparative XPS study provides first direct experimental evidence for cation-anion charge-transfer phenomena in ionic liquids as a function of the ionic liquid's anion. These charge-transfer effects are found to be surprisingly similar for [C8C1Im]+ and [C8C1C 1Im]+ salts of the same anion, which in combination with theoretical calculations leads to the conclusion that hydrogen bonding and charge transfer occur independently from each other, but are both more pronounced for small and more strongly coordinating anions, and are greatly reduced in the case of large and weakly coordinating anions. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Thomas M.,University of Bonn | Brehm M.,Wilhelm Ostwald Institute For Physikalische Und Theoretische Chemie | Holloczki O.,University of Bonn | Kelemen Z.,Budapest University of Technology and Economics | And 3 more authors.
Journal of Chemical Physics | Year: 2014

The vibrational spectra of the ionic liquid 1-ethyl-3-methylimidazolium acetate and its mixtures with water and carbon dioxide are calculated using ab initio molecular dynamics simulations, and the results are compared to experimental data. The new implementation of a normal coordinate analysis in the trajectory analyzer TRAVIS is used to assign the experimentally observed bands to specific molecular vibrations. The applied computational approaches prove to be particularly suitable for the modeling of bulk phase effects on vibrational spectra, which are highly important for the discussion of the microscopic structure in systems with a strong dynamic network of intermolecular interactions, such as ionic liquids. © 2014 AIP Publishing LLC. Source

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