Molecular dynamics simulations of 1,2-disubstituted (hydroxy- and amino-) ethanes: Pure molecular liquids and their aqueous solutions.
Date
2003
Authors
Gubskaya, Anna V.
Journal Title
Journal ISSN
Volume Title
Publisher
Dalhousie University
Abstract
Description
This thesis is a comparative computational study of the local structure of three widely used representatives of 1,2-disubstituted ethanes, namely ethylene glycol (EG), ethylenediamine (ED) and 2-aminoethanol (AE), in liquid state and their mixtures with water. Classical molecular dynamics combined with three-dimensional atomic density maps, known as spatial distribution functions (SDF's), are the computational tools used in this study.
The present work consists of three parts. In the first part, twelve molecular models were designed and gas-phase simulations were carried out for each. The results obtained were compared with the most reliable experimental estimates in order to test different force fields and molecular representations. In the second part liquid-phase simulations were performed on the most successful (AMBER/OPLS-based) models. The heats of vaporization and self-diffusion coefficients were used as criteria for the final selection of molecular models to be employed in the subsequent simulations of aqueous solutions.
In the third part, a detailed structural analysis was performed. As an essential part of this analysis the dihedral angle distributions were calculated and relative populations of conformers with respect to the central dihedral angle were determined for pure EG, ED and AE, as well as their mixtures with water, where four compositions of each compound were considered. It has been confirmed that in the liquid phase the gauche conformation accounts for the major population of rotational isomers for EG and AE, while ED exhibits a significant population of trans conformers. Additionally, the first theoretical estimates of the compositional dependence of self-diffusion coefficients for the aqueous solutions of EG, ED and AE were obtained. The analysis of radial distribution functions in conjunction with calculated numbers of nearest neighbors around oxygen and nitrogen atoms of the main functional groups provided some structural insights into the H-bonding pattern of the systems studied. (Abstract shortened by UMI.)
Thesis (Ph.D.)--Dalhousie University (Canada), 2003.
The present work consists of three parts. In the first part, twelve molecular models were designed and gas-phase simulations were carried out for each. The results obtained were compared with the most reliable experimental estimates in order to test different force fields and molecular representations. In the second part liquid-phase simulations were performed on the most successful (AMBER/OPLS-based) models. The heats of vaporization and self-diffusion coefficients were used as criteria for the final selection of molecular models to be employed in the subsequent simulations of aqueous solutions.
In the third part, a detailed structural analysis was performed. As an essential part of this analysis the dihedral angle distributions were calculated and relative populations of conformers with respect to the central dihedral angle were determined for pure EG, ED and AE, as well as their mixtures with water, where four compositions of each compound were considered. It has been confirmed that in the liquid phase the gauche conformation accounts for the major population of rotational isomers for EG and AE, while ED exhibits a significant population of trans conformers. Additionally, the first theoretical estimates of the compositional dependence of self-diffusion coefficients for the aqueous solutions of EG, ED and AE were obtained. The analysis of radial distribution functions in conjunction with calculated numbers of nearest neighbors around oxygen and nitrogen atoms of the main functional groups provided some structural insights into the H-bonding pattern of the systems studied. (Abstract shortened by UMI.)
Thesis (Ph.D.)--Dalhousie University (Canada), 2003.
Keywords
Chemistry, Physical.