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Molecular simulations of water - rutil interface
Hanke, Hynek ; Předota, Milan (advisor) ; Lísal, Martin (referee)
Study of structural and particularly dynamical properties of the interface of water with graphite and rutile surfaces points towards anomalous behavior of water molecules close to solid matter. Evaluation of statistical properties like translational and rotational diffusivity, residence times and autocorrelation functions of orientation vectors indicates that the translation and rotation of water molecules can be not only hindered, but also facilitated, according to the particular local density, interactions and and geometrical structure of the surface. The newly developed methods for the measurement of statistical rotational properties near to liquid-solid boundary overcomes the difficulties that are closely related to the measurement of dynamical properties in strongly inhomogeneous environment in a way, that can be applied to other model systems of this type.
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Linear semiflexible polyelectrolytes in solutions
Bačová, Petra ; Limpouchová, Zuzana (advisor) ; Lísal, Martin (referee)
Title: Linear semiflexible polyelectrolytes in solutions Author: Petra Bačová Department: Faculty of Science, Charles University in Prague Supervisor: Doc. Ing. Zuzana Limpouchová, CSc. Supervisor's e-mail address: zl@vivien.natur.cuni.cz Consultant: Mgr. Peter Košovan, PhD. Abstract: In this thesis I used the Molecular dynamics simulations for study of charged polymers (polyelectrolytes) and their behaviour in solutions. Wide range of polyelectrolytes are se- miflexible and in contrast to neutral polymers it is possible to influence their stiffness by changing the properties of solution as for example ionic strength. The chain flexibility may be characterized by the persistence length. Thesis explains how to express the persistence length from orientational correlation function which shows the double exponential decay. Two contributions to chain stiffness are discussed and the interest is concentrated around electrostatic persistence length which seems to be scale dependent. An effect of added salt on the chain conformation is studied. Salt is treated implicitly within the Debye-Hückel approximation. The results are confronted with OSF theory and the conclusions of vari- ational calculations of Maghi and Netz. The presented thesis describes the conformational behaviour of polyelectrolytes in salty solutions,...
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Scaling Laws for Polymers in Dissipative Particle Dynamics Revised
Posel, Z. ; Lísal, Martin
We present here a systematic study of dynamic behavior for polymer (PE) melt by means of Dissipative Particle Dynamics (DPD). We used DPD spring potential between adjacent segments. By changing various parameters related to spring potential like stiffness k, equilibrium distance r0 and parameters related to dynamic behavior like friction coefficient γ presented in dissipation force we tested their influence on scaling laws. We also compared these scaling laws obtained from our simulations with predictions from Rouse theory.
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Nedávné pokroky v molekulárních simulacích termodynamického chování tekutých soustav.
Aim, Karel ; Lísal, Martin ; Nezbeda, Ivo ; Ungerer, P. ; Teuler, J.-M. ; Rousseau, B.
An overview of the recent developments in molecular computer simulation techniques used to calculate phase equilibria and thermodynamic properties of fluid systems is given. Particular attention is paid to the methodologies as follows: (i) reaction Gibbs ensemble Monte Carlo (RGEMC), which allows accurate phase equilibrium predictions for mixtures by employing experimental pure-component vapour pressure data in the computational procedure (ii) direct Monte Carlo simulation of Joule-Thomson processes, (iii) Monte Carlo simulations at fixed entropy, and (iv) an implemented parallelized sampling version of the Gibbs ensemble Monte Carlo (GEMC), which by-passes the physical transfer of complex molecules between boxes representing different phases by computing the chemical potential in an NVT ensemble (and is applicable also to flexible molecules). Example applications of the considered techniques for real fluid systems ar
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