DRAG-ASSISTED SIMULATED ANNEALING METHOD FOR GEOMETRY OPTIMIZATION OF MOLECULAR SYSTEMS
Bilguun Woods1, Paulo Acioli2, David Capota2.
Northeastern Illinois University, Chicago, IL.
One of the methods to find the global minimum of a potential energy surface of a molecular system is simulated annealing. In molecular dynamics the system is initially at a high temperature and then slowly cooled off so there is a chance to explore the different degrees of freedom and ultimately find the global minimum. One of the most traditional methods was first implemented by Woodcock in 1971. In this method, the velocities are scaled down after a given number of molecular dynamics steps. In this work we propose to use a viscous friction term, similar to the one use in Langevin dynamics, to slowly bring down the temperature of the system in a natural way. The linear drag term, which is proportional to the velocity, will become 0 when the system reaches a minimum. We tested the method in Lennard-Jones clusters of up to 21 atoms. We started the system in different initial conditions and used different values for the temperature and the drag coefficient and found the global minima of each cluster. This method is conceptually very simple, but very robust in finding the global minima.