Doctoral Dissertations

Pauf Neupane

Keywords and Phrases

Alkane Freezing; Contact angle; Molecular Dynamics; Nanodroplet Structure; Spreading; Wetting

Abstract

“The wetting behavior of aqueous organic systems is of great importance in several environmental and industrial processes such as the formation and growth of atmospheric aerosols, crude oil recovery from an oil field, onsite cleaning of natural gas, and clean-up of oil spills. In this work, we employed molecular dynamics (MD) simulations to explore the temperature dependent wetting behavior of octane and nonane on water in planar interfaces as well as in nanodroplets using PYS alkane and SPC/E and TIP4P/2005 water models.

For planar interfaces, we found unusual wetting behavior of octane and nonane on SPC/E water, but generally not on TIP4P/2005 water, at lower temperatures, where the spreading coefficient decreased and the contact angle increased with increasing temperature. At higher temperatures, these contact angles were found to decrease with increasing temperatures as the usual high temperature wetting transition was approached.

For nanodroplets, the contact angle of octane and nonane on both SPC/E and TIP4P/2005 water was found to unusually increase with increasing temperature. Configurational fluctuations of the nanodroplets were found to be greatly reduced for larger values of the potential cut-off radius. Moreover, the contact angles were calculated for different ratios of octane and water and found to be nearly independent of the liquid species ratio.

In addition, we also studied the physical properties as well as molecular orientations of octane and nonane using PYS, NERD and a modified TraPPE-UA alkane model. Molecular orientations were found to be temperature dependent in the liquid-vapor interface, but not in the bulk region. At lower temperatures, the mean molecular orientation was more perpendicular to the surface on the liquid side of the Gibbs dividing surface and more parallel to the surface on the vapor side. These orientational trends were mirrored in the freezing of NERD octane and nonane at 195 K and 210 K, respectively, with the oriented surface layer freezing first”--Abstract, page iv.

Advisor(s)

Wilemski, Gerald

Committee Member(s)

Medvedeva, Julia E.
Parris, Paul Ernest, 1954-
Vojta, Thomas
Wyslouzil, Barbara

Department(s)

Physics

Degree Name

Ph. D. in Physics

Publisher

Missouri University of Science and Technology

Publication Date

Fall 2020

Journal article titles appearing in thesis/dissertation

  • Properties and freezing at the liquid-vapor interface of n-octane and n-nonane from molecular dynamics simulations
  • Molecular dynamics study of temperature dependent wetting in alkane-water systems
  • Temperature dependent wetting and structure of alkane-water nanodroplets

Pagination

xiv, 92 pages

Note about bibliography

Includes bibliographic references.

Rights

© 2020 Pauf Neupane, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11796

Electronic OCLC #

1240361938

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Physics Commons

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