Molecular Dynamics Simulations of Solutes in Liquid Water and at the Ice/water Interface.

                 

Principal Investigator

Anthony Haymet

School of Chemistry,

University of Sydney

Solutes have a huge impact on the thermodynamicproperties of both solid and liquid water. These solutes have important biological and technological applications. In this project we will perform molecular dynamics (MD) on model systems including inert gases and electrolytes in water and at the ice/water interface. We also aim to model an 'antifreeze' protein at the ice/water interface. We will calculate static properties such as the pair correlation functions and the density profile as well as thermodynamic properties such as entropy, free energy and the potential of mean force.  

Co-Investigators

     

Jennifer Hayward

Andrew Eaton

Michael Booth

David Fang

School of Chemistry,

University of Sydney

     
             

   
             

Projects

g59 - VPP

           
                 

What are the results to date and the future of this work?

Extensive development and testing of the original molecular dynamics (MD) code has been undertaken. The changes have generated several versions of the code to handle the different aspects of our ongoing aims and objectives. These changes include the ability to simulate in flexible cell sizes and shapes in both NVE and NPT ensembles, the inclusion of the pressure tensor, modifications to allow the measurement of thermodynamic properties and the ability to simulate water and ice/water interfaces with a wide range of solute particles, both charged and uncharged.

Simulations have been performed to study the ice/water interface. Three different ice/water interfaces (the prism, basal and [2021] interfaces) have been generated and extensive work has been carried out in order to equilibrate these systems. Consultation with VPP staff, including attendance at the VPP vectorisation course in February 1997, has resulted in a dramatic improvement to the level of vectorisation of the code, bringing it to around 99% vectorised.

Future work aims to finalise the equilibration and measure a wide range of properties of the interfaces for publication. The recently developed version of the code for simulating solutes at the ice/water interface will be implemented to achieve our objectives regarding these systems. Subject to computing resources, the project will be completed in August 1998 coinciding with the submission of Ph.D theses by several of the co-investigators.

                 
Appendix B -

                 

     

What computational techniques are used?

Our simulations solve first order differential equations (Hamilton's equations of motion) using a fifth value Gear Predictor Corrector algorithm. Long range charge-charge interactions are handled using the Ewald summation technique.

Publications

J. A. Hayward, A. D. J Haymet, Molecular Dynamics Simulations of Ice-1h/Water Interfaces, Poster presentation at the Molecular Liquids: Orientational Order and Dynamics in Liquids and Glasses Conference held in September 1997 in Greece.

     
- Appendix B