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Research of the Centre for Molecular Simulation


Background

The research of the Centre for Molecular Simulation  is unique among computer science departments in Australian Universities. The main focus of its activities is the application of computing methods to solve research problems in the physical sciences and engineering. Consequently, a multidisciplinary approach is used with input from the fields of mathematics, physics,chemistry and chemical engineering in addition to computer science. Work is currently being conducted on aspects of molecular simulation, phase transitions, membrane equilibria, ionic fluids, polymer science and nanotechnology. Examples of research projects are given below.


Molecular Simulation

Equilibrium Simulations

The Gibbs Ensemble Monte Carlo algorithm has been implemented for the prediction of phase equilibria in multiphase and multicomponent fluids. Historically, the prediction of both vapour-liquid and liquid-liquid equilibria has relied almost exclusively on approximate theoretical models or on empirical equations of state rather than on rigorous models for intermolecular interaction at high fluid densities. The advent of new computer simulation techniques provides an opportunity to apply directly our knowledge of intermolecular potentials to the prediction of fluid phase equilibria. This work has several strands.

  • Investigation of three-body interactions in pure fluids. This work has found that three-body repulsion has an important role in determining phase vapour-liquid transitions.The role of three-body interactions on vapour-liquid and liquid-liquid equilibria in binary mixtures.Simulation of membrane equilibria.Simulation of flexible hard-sphere chains and ionic systems.

  • High pressure liquid-liquid phase equilibria.


Non-Equilibrium Molecular Dynamics

While thermodyanmics traditionally deals with systems that are at equilibrium, most natural systems are actually far from equilibrium and are either evolving with time, or exist in a time-independent steady state. One can study such systems at the microscopic level by applying the principles of nonequilibrium statistical mechanics to molecular dynamics simulations. Some of the work we are currently interested in includes:

  • Development of new algorithms for simulating simple and complex fluids far from equilibrium. Molecular rheology of polymer melts. Transport properties of bulk and microscopically confined fluids.

  • Relationship between microscopic dynamics and irreversible thermodynamics.


Nanotechnology

We are interested in using molecular simulation and other computational techniques to gain theoretical insights into how nanosystems work. For example we are currently working on the simulation of a particular type of biomolecular rotary motor, ATP-ase. This biological molecule acts both as a proton pump (pumping H+ ions between different parts of a cell, thus moderating intracellular PH levels), as well as having the remarkable ability to move in a direction perpendicular to the axis of rotation (similar to the movement of a helicopter). The mechanisms of this behaviour are cuurently being examined with the aim of developing a model to account for the translational motion of the motor. This could potentially a very useful applications in molecular medicine.


Molecular Simulation of Spectra

Molecular spectroscopy is an accurate and powerful technique to probe molecular structural information and more importantly, inter- and intra- molecular interactions of molecular species. This project focuses on the quantum mechanical/dynamical simulation for small molecular species, Van der Waals (VdW) complexes and other organic compunds for their microwave (MW), far-infrared (IR), IR, X-ray absorption and emission as well as electron momentum spectroscopy (EMS). This project covers a wide spectrum of the molecular spectroscopy and potential energy surfaces (PES). For example, MW and far-IR simulation provide accurate information for the energy well bottom region of the PES, whereas IR determines the accuracy of the attractive wall of a PES. X-ray provides information of both the ground and the excited electronic states as well as a particular molecular orbital (MO) information in coordinate space; EMS offers unique novel information of the MOs and the quality of the basis functions.


 Thermodynamics and Statistical Mechanics

The results of molecular simulation studies are also being used to improve the traditional basis of thermodynamic prediction. Work is currently in progress in the following areas.

  • High pressure phase equilibria of binary and ternary mixtures.Intermolecular interactions in aqueous systems.Combining rules and mixture prescriptions.

  • Equations of state for ionic systems and polymer fluids.