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Aysa Akad Galbraith

Ph.D. Chemical Engineering, May 2006
North Carolina State University

M.S. Chemical Engineering, December 2002
North Carolina State University

B.S Chemical Engineering, May 2000
Bosphorus University, Turkey 


Thesis Title: Phase Equilibria of Diatomic Lennard-Jones Molecules Using Monte Carlo Simulation

Advisor: Carol K. Hall

Systems of Interest:

Methods:

  • Solid-liquid and Vapor-liquid Phase Equilibria
  • Chiral Molecules

  • Monte Carlo Simulations
  • Gibbs-Duhem Integration
  • Frenkel-Ladd Free Energy Calculations

Abstract:

Crystallization is a separation and purification process used widely throughout the chemical industry during the synthesis of different types of materials. This process is especially important in the pharmaceutical industry where it is used in the separation of racemic mixtures to produce single enantiomeric drugs such as ketoprofen. The fundamental information needed to achieve a successful level of separation of mixtures is provided by phase diagrams. Molecular modeling and simulations of systems containing small rigid molecules can provide useful information that leads to a better understanding of the thermodynamics and structural properties of such systems.

The overall aim of this research has been to gain an understanding of the nature of phase equilibria. We have used Monte Carlo computer simulation to explore the vapor-liquid and solid-liquid phase behavior of simple nonspherical molecules.

We have described the application of the Gibbs-Duhem integration technique combined with Monte Carlo simulations to predict solid-liquid and vapor-liquid phase diagrams for binary mixtures containing nonspherical molecules interacting via Lennard-Jones potentials. The Gibbs-Duhem integration technique was chosen for this study because it enables direct calculation of solid-liquid phase equilibria while avoiding the problems associated with particle insertions into dense solid phases found with Gibbs ensemble methods. We have calculated phase diagrams for pure components and binary mixtures containing Lennard-Jones dumbbells. We also have explored the effect of varying the molecular size, intermolecular attractions and binary interaction parameter on the dumbbell mixture's phase behavior. The thermodynamic integration method developed by Frenkel and Ladd has been used to calculate the free energy during the solid-liquid phase calculations, which helped us to determine the most stable solid phase. In the future, these calculations can be extended to a simple binary diastereomer mixture, such as (2S,3R)-2-chloro-3-butanol and (2R,3R)-2-chloro-3-butanol.

Presentations

A. L. Akad, C. K. Hall, "Monte Carlo Simulations of Phase Diagrams for Diastereomeric Molecules" poster presentation at the Schoenborn Competition, November 10, 2003, Raleigh, NC.

A. L. Akad, C. K. Hall, "Monte Carlo Simulations of Phase Equlibria for Diatomic Lennard-Jones Molecules" oral presentation at the AICHE Annual Meeting, November 19, 2003, San Francisco, CA.

A. L. Akad, C. K. Hall, "Monte Carlo Simulations of Phase Diagrams for Diastereomeric Molecules" poster presentation at the 10th PPEPPD Conference, May 18, 2004, Snowbird, UT.

A. L. Akad, C. K. Hall, "Monte Carlo Simulations of Phase Equlibria for Mixtures Containing Nonspherical Lennard-Jones Molecules" oral presentation at the AICHE Annual Meeting, November 7, 2004, Austin, TX.

Publications

A. L. Galbraith, C. K. Hall, "Vapor-liquid Phase Equilibria for Mixtures Containing Diatomic Lennard-Jones Molecules" Fluid Phase Equilibria 241 175-185 (2006).

A. L. Galbraith, C. K. Hall, "Solid-liquid Phase Equilibria for Mixtures Containing Diatomic Lennard-Jones Molecules" (in preparation).







alakad@unity.ncsu.edu