טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentPeleg Adi
SubjectMolecular Simulation of Surface Tension of Lennard-Jones
Liquids
DepartmentDepartment of Chemical Engineering
Supervisors Professor Simcha Srebnik
Professor Simon Brandon
Professor Emeritus Abraham Marmur
Full Thesis textFull thesis text - English Version


Abstract

Our thesis focuses on Monte Carlo simulations that are used to characterize a system in equilibrium to find the surface tension in planar surfaces such as films.

In previous years several ways to calculate the surface tension between liquid-fluid systems were developed. The main method for those calculations was the stress tensor which is also referred to as the Irving Kirkwood (IK) method. This is a molecular point of view method that calculates the surface tension as the integral of the difference between the normal and tangential parts of the stress tensor. The long range correction (LRC) was a very important addition to the energy and press tensor. The LRC is essential in truncated potential simulations to fix the deviation of the properties of the system caused by the discontinuous behavior of the potential. Without it the normal component was not constant as it should be for a system in equilibrium and the surface tension value was smaller than in experiments and not similar for different potential cut-offs.

This thesis addresses a thermodynamic method for the surface tension calculations referred to as the Gibbs method. This method is based on a model in which the surface tension is regarded as the difference between the energy in a real system and the energy in an idealized system in which two phases retain their bulk composition all the way up to the mathematical interface to be characterized by zero thickness and placed in an arbitrary position in between the two phases. In our thesis this position is set to be the equimolecular position. The well studied stress tensor method mentioned above was used as a source of comparison to the Gibbs method.