Mapping saddles and minima on free energy surfaces using multiple climbing strings

Area of Science:

• Computational Chemistry
• Molecular Dynamics
• Statistical Mechanics

Background:

• Characterizing multistate transitions in molecular systems requires locating saddle points on free energy surfaces.
• Saddle points represent transition states, necessitating pathways and free energy measurements for rate estimation.

Purpose of the Study:

• To develop a new multistring version of the climbing string method for locating all saddle points and pathways on free energy surfaces.
• To improve the characterization of transition states and free energy landscapes in complex molecular systems.

Main Methods:

• The proposed method utilizes dynamic strings to find saddle points and static strings to store converged pathways.
• Interaction between dynamic and static strings prevents convergence to previously identified saddles.
• Free energy is measured along the strings, guaranteeing identification of connected minima.

Main Results:

• The method successfully maps networks of stationary points on 2D and 4D free energy surfaces.
• Demonstrated application on alanine dipeptide and alanine tripeptide systems.

Conclusions:

• The multistring climbing string method offers a robust approach for exploring complex free energy landscapes.
• This technique is crucial for accurate estimation of transition rates in molecular systems.