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Solvation thermodynamic properties from molecular dynamics on the terahertz time scale

Bernhardt, Marvin (2016):
Solvation thermodynamic properties from molecular dynamics on the terahertz time scale.
Darmstadt, Technische Universität, [Online-Edition: http://tuprints.ulb.tu-darmstadt.de/6042],
[Master Thesis]

Abstract

The Two-Phase Thermodynamic (2PT) model describes an arbitrary system as a superpositon of a hard-sphere gas and a solid, enabling us to calculate the system's entropy, thereby making a connection from the dynamics to the thermodynamics. In this work the 2PT model is used to investigate effects of solutes on the dynamics and thermodynamics of water. The negative excess mixing entropy of water-methanol and water-ethanol mixtures are correctly predicted by the model and accounted to the lowered diffusion of the molecules in the mixture. Ethanol is found to lower the entropy of water more than methanol. A second system analyzed are aqueous solutions of sodium chloride. Increasing salt concentrations are shifting diffusional modes of water to oscillations and lower its entropy. Several problems of the 2PT model are pointed out which are related to the unphysical separation in two subsystems. Deviating separation schemes based on time separation, velocity separation and position separation are proposed and analyzed.

Item Type: Master Thesis
Erschienen: 2016
Creators: Bernhardt, Marvin
Title: Solvation thermodynamic properties from molecular dynamics on the terahertz time scale
Language: English
Abstract:

The Two-Phase Thermodynamic (2PT) model describes an arbitrary system as a superpositon of a hard-sphere gas and a solid, enabling us to calculate the system's entropy, thereby making a connection from the dynamics to the thermodynamics. In this work the 2PT model is used to investigate effects of solutes on the dynamics and thermodynamics of water. The negative excess mixing entropy of water-methanol and water-ethanol mixtures are correctly predicted by the model and accounted to the lowered diffusion of the molecules in the mixture. Ethanol is found to lower the entropy of water more than methanol. A second system analyzed are aqueous solutions of sodium chloride. Increasing salt concentrations are shifting diffusional modes of water to oscillations and lower its entropy. Several problems of the 2PT model are pointed out which are related to the unphysical separation in two subsystems. Deviating separation schemes based on time separation, velocity separation and position separation are proposed and analyzed.

Place of Publication: Darmstadt
Divisions: 07 Department of Chemistry > Computational Physical Chemistry
07 Department of Chemistry
Date Deposited: 09 Jul 2017 19:55
Official URL: http://tuprints.ulb.tu-darmstadt.de/6042
URN: urn:nbn:de:tuda-tuprints-60421
Referees: van der Vegt, Prof. Dr. Nico and Dalgicdir, Dr. Cahit
Refereed / Verteidigung / mdl. Prüfung: January 2017
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