Atomistic simulations of rare events using gentlest ascent dynamics

Area of Science:

• Computational physics and chemistry
• Materials science
• Statistical mechanics

Background:

• Complex systems dynamics involve thermally activated barrier crossing events.
• Simulating these events is challenging for conventional methods like molecular dynamics.
• Gentlest ascent dynamics (GAD) was previously developed to describe system escape from attraction basins.

Purpose of the Study:

• To extend GAD for finite temperature simulations, allowing systems to hop between saddle points.
• To propose a strategy for sampling low barrier saddle points near stable configurations.
• To demonstrate the method's utility in studying point defect activity on surfaces.

Main Methods:

• Extension of gentlest ascent dynamics (GAD) for finite temperature simulations.
• Development of a strategy to sample an ensemble of low barrier saddle points.
• Application to model systems involving surface point defects.

Main Results:

• The extended GAD successfully enables finite temperature simulations of barrier crossing.
• The proposed strategy effectively samples low barrier saddle points.
• The method's utility is demonstrated for surface vacancy/ad-atom pairs and heptamer islands on copper (111).

Conclusions:

• The enhanced GAD provides an effective approach for simulating thermally activated processes in complex systems.
• This method facilitates the study of low barrier saddle points and their role in phenomena like point defect activity.
• The findings offer a valuable tool for computational materials science and condensed matter physics.