Structural and Thermodynamic properties of CS-fluids: A Molecular Dynamics Study

Pant, Shashank (2015) Structural and Thermodynamic properties of CS-fluids: A Molecular Dynamics Study. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MS dissertation of Shashank Pant (10MS27)) MS_Thesis_Shashank_Pant.pdf - Submitted Version Restricted to Repository staff only Download (2MB)

Abstract

This thesis applies statistical physics approach combined with computer simulations to investigate the changes in the properties of coarse grained CS fluids under confinement inside carbon nanotubes and around non-polar hydrophobic solutes. In Chapter 1, we have given a very general introduction about the Water, various potential forms available for studying water and also the development of new coarse grained potential models and their power in reproducing water and water-like anomalies. Lastly at the end of the chapter we have we have introduced briefly the concept of coarse-graining and emphasized on its procedure. In Chapter 2, we have summarized various techniques available to perform Molecular Dynamics Simulations. Briefly highlighting the main concept of PBC, potential truncation, widom particle insertion method and very recently developed cell theory. In chapter 3, we have used coarse grained water model CS fluid potential and studied its structuring inside carbon nanotubes of varying diameter. We have shown the confined CS fluids are well ordered and it results in the formation of range of structures inside CNT from 1-D CS-fluid wires to N-gonal helical structures to bulk like CS-fluids. We have shown inside bigger CNT two types of CS-fluids are present one at the interface of CNT and other at the centre of CNT. Further calculating correlation parameter we showed the two CS-fluids are different from each other. In Chapter 4, we have used 6, 6 CNT and calculated various thermodynamics and structural properties of confined CS-fluids. In translational order parameter and excess entropy calculations we observe new anomalous region which has no dependence on the CS-fluid potential parameters. We observe new anomalous regions of CS-fluids inside (6, 6) CNTs. In Chapter 5, we try to present a generalized approach of defining hydrophobicity by considering spherical non-polar solutes in coarse grained CS-fluids and studied the importance of various parameters like degree of hydrophobicity, temperature. We used a very old approach of calculating entropy by particle insertion method i.e. widom particle insertion method and showed the changes in entropy of CS-fluids in the first hydration shell of the non-polar solutes. Finally I talk about some myths present in our current understanding about water models and hydrophobicity.

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