Universität zu Köln

Coskuner, Orkide (2003). Investigation of Hydrophobic Interactions by Monte Carlo Simulation. PhD thesis, Universität zu Köln.

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Abstract

In this work the temperature and pressure dependence of the hydrophobic effects have been investigated. For this purpose, the structural and thermodynamic properties of the apolar and water molecules, with increasing temperature or pressure, have been calculated by Monte Carlo simulations. The TIP5P model for the water dimer was optimized by ab initio calculations. To investigate the hydrophobic effects an NPT ensemble MC program was implemented in C. The hydrophobic interactions have been studied by the addition of two methane, two ethane and two xenon into 216 water molecules. To compare the change in the physical properties of water when these apolar molecules are added, pure water simulations with 216 water molecules were performed under same conditions. The contact pair probability is higher for the ethane molecules. The correlation functions indicate that the water molecules rearrange and reorganize with increasing temperature. To generate a new view of the temperature dependence of apolar molecules effects on water, the thermodynamic properties of water have been calculated. The changes are large for water-ethane system. To investigate the residual chemical potential of the highly dense systems, different methods have been studied in this work. It has been found that the Widom insertion method yields the closest approximations to the experimental data.