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Molekulové simulace nukleace ledu
Pluhařová, Eva ; Jungwirth, Pavel (advisor) ; Kolafa, Jiří (referee)
Title: Molecular simulations of ice nucleation Author: Eva Pluhařová Department: Department of Physical and Macromolecular Chemistry Faculty of Science UK Advisor: doc. Mgr. Pavel Jungwirth, DSc., IOCB AS CR, v.v.i. Advisor's e-mail address: pavel.jungwirth@uochb.cas.cz Abstract: By means of molecular dynamics simulations we have systematically investigated homogeneous ice nucleation in neat and surface contaminated water. As models of the adsorbates we have assumed pentanol and pentanoic acid. In neat water nucleation preferentially starts in the subsurface region, which accommodates better than the bulk the volume increase associated with freezing. Homogeneous ice nucleation is affected more by alcohol than by acid. Water slabs covered by a disordered layer of pentanol exhibit negligible preference for subsurface nucleation and longer nucleation times in comparison with neat water, while nucleation times are almost unaffected by the presence of pentanoic acid and the subsurface preference is only slightly decreased. We tried to rationalize the differences between the effects of different compounds by their ability to orient water molecules and to change their mobility. The fact that adsorbates differ in the influence on homogeneous ice nucleation has important implications for the microphysics of...
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Solvent effects on ion pairing and photoionization in water
Pluhařová, Eva ; Jungwirth, Pavel (advisor) ; Nachtigall, Petr (referee) ; Laage, Damien (referee)
Title: Solvent effects on ion pairing and photoionization in water Author: Mgr. et Ing. Eva Pluhařová Department: Physical and Macromoleculer Chemistry Advisor: Prof. Pavel Jungwirth, DSc., IOCB AS CR, v.v.i. Advisor's e-mail address: pavel.jungwirth@uochb.cas.cz Abstract: Various methods of theoretical chemistry, namely classical molecular dynamics simulations with empirical force fields, ab initio molecular dynamics, enhanced sampling methods, and ab initio calculations were used to provide new insight into ion pairing and photoionization in aqueous solutions. Systems mod- eling aqueous solutions of decreasing size were investigated by computational methods of increasing level of sophistication. In a classical molecular dynamics study of concentrated lithium salt solutions, the electronic continuum correction to account for polarization provided qualita- tive improvement over the conventional non-polarizable force fields and enabled molecular interpretation of neutron scattering measurements. The same model- ing approach was also successful in predicting the affinity of halide ions to the solution/oil interface. By combining ab initio molecular dynamics and potential of mean force cal- culations, we designed a reliable computational protocol for calculating the free energy profile for an ion pair...
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Molekulové simulace nukleace ledu
Pluhařová, Eva ; Kolafa, Jiří (referee) ; Jungwirth, Pavel (advisor)
Title: Molecular simulations of ice nucleation Author: Eva Pluhařová Department: Department of Physical and Macromolecular Chemistry Faculty of Science UK Advisor: doc. Mgr. Pavel Jungwirth, DSc., IOCB AS CR, v.v.i. Advisor's e-mail address: pavel.jungwirth@uochb.cas.cz Abstract: By means of molecular dynamics simulations we have systematically investigated homogeneous ice nucleation in neat and surface contaminated water. As models of the adsorbates we have assumed pentanol and pentanoic acid. In neat water nucleation preferentially starts in the subsurface region, which accommodates better than the bulk the volume increase associated with freezing. Homogeneous ice nucleation is affected more by alcohol than by acid. Water slabs covered by a disordered layer of pentanol exhibit negligible preference for subsurface nucleation and longer nucleation times in comparison with neat water, while nucleation times are almost unaffected by the presence of pentanoic acid and the subsurface preference is only slightly decreased. We tried to rationalize the differences between the effects of different compounds by their ability to orient water molecules and to change their mobility. The fact that adsorbates differ in the influence on homogeneous ice nucleation has important implications for the microphysics of...
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