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- Amira, S., et al.
(författare)
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Car-Parrinello molecular dynamics simulation of Fe3+(aq)
- 2005
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 109:29, s. 14235-14242
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Tidskriftsartikel (refereegranskat)abstract
- The optimized geometry and energetic properties of Fe(D2O)(n)(3+) clusters, with n = 4 and 6, have been studied with density-functional theory calculations and the BLYP functional, and the hydration of a single Fell ion in a periodic box with 32 water molecules at room temperature has been studied with Car-Parrinello molecular dynamics and the same functional. We have compared the results from the CPMD simulation with classical MD simulations, using a flexible SPC-based water model and the same number of water molecules, to evaluate the relative strengths and weaknesses of the two MD methods. The classical MD simulations and the CPMD simulations both give Fe-water distances in good agreement with experiment, but for the intramolecular vibrations, the classical MD yields considerably better absolute frequencies and ion-induced frequency shifts. On the other hand, the CPMD method performs considerably better than the classical MD in describing the intramolecular geometry of the water molecule in the first hydration shell and the average first shell(...)second shell hydrogen-bond distance. Differences between the two methods are also found with respect to the second-shell water orientations. The effect of the small box size (32 vs 512 water molecules) was evaluated by comparing results from classical simulations using different box sizes; non-negligible effects are found for the ion-water distance and the tilt angles of the water molecules in the second hydration shell and for the O-D stretching vibrational frequencies of the water molecules in the first hydration shell.
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- Amira, S., et al.
(författare)
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Molecular dynamics simulation of Fe2+(aq) and Fe3+(aq)
- 2004
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 108:1, s. 496-502
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations of single-ion Fe2+(aq) and Fe3+(aq) solutions have been performed with two rigid-water models (SPC and SPC/E) and a newly constructed SPC-based flexible-water model (SPC+CCL). The SPC+CCL water model in combination with effective Fe2+ and Fe3+ ion-water potentials manages to reproduce many experimental structural and dynamical properties of the solutions. Special attention is given to the large ion-induced frequency shifts of the OH stretching bands, which are also well reproduced by the SPC+CCL model.
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- Gotte, A., et al.
(författare)
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Molecular dynamics study of oxygen self-diffusion in reduced CeO2
- 2007
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Ingår i: Solid State Ionics. - : Elsevier BV. - 0167-2738 .- 1872-7689. ; 178:25-26, s. 1421-1427
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Tidskriftsartikel (refereegranskat)abstract
- The oxygen self-diffusion in partially reduced CeO2 has been investigated by large-scale Molecular Dynamics simulations, in the temperature range between 800 and 2200 K. Simulation boxes with similar to 4100 and similar to 33,000 ions were investigated for randomly distributed oxygen vacancies and Ce3+ ions. Our calculated self-diffusion coefficients vary between 10(-8) and 10(-6) cm(2)/s in the temperature range studied. The activation energy and D-0 values are also reported. The oxygen diffusion mechanism has also been analyzed: only a (< 100 > vacancy mechanism is observed.
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- Zöttl, S., et al.
(författare)
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Energy harvesting in doped helium nano-droplets
- 2012
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Ingår i: Journal of Physics, Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 388:13, s. 132003-
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Tidskriftsartikel (refereegranskat)abstract
- We report the observation of sequential Penning ionization of dopants by metastable helium atoms in helium nano-droplets resulting in doubly charged ions. Strong charge induced dipole-interaction between the excited helium atom and the target ion provides a high probability for the transfer of the internal energy of the excited helium atom to the dopant ion. This process may also lead subsequently to a Coulomb explosion of molecular or cluster dopants.
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