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Sampling free energy surfaces as slices by combining umbrella sampling and metadynamics
Shalini Awasthi1, Venkat Kapil1, Nisanth N Nair1
1Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, 208016, India.
Journal of Computational Chemistry
|April 10, 2016
Summary
This study introduces a novel hybrid metadynamics and umbrella sampling method for efficient free energy landscape calculations. The combined approach significantly speeds up the sampling of complex chemical reactions and conformational changes.
Area of Science:
- Computational Chemistry
- Molecular Dynamics Simulations
- Free Energy Calculations
Background:
- Metadynamics (MTD) is effective for sampling high-dimensional free energy landscapes but struggles with flat or unbound wells.
- Standard MTD can be computationally expensive for complex systems requiring extensive sampling.
- Efficient sampling of free energy surfaces is crucial for understanding chemical reactions and conformational changes.
Purpose of the Study:
- To develop a computationally efficient method for sampling complex free energy landscapes.
- To combine Metadynamics (MTD) with Umbrella Sampling (US) for enhanced sampling of orthogonal collective variables (CVs).
- To enable accurate free energy calculations for challenging systems using ab initio and QM/MM molecular dynamics.
Main Methods:
- Integration of Umbrella Sampling (US) potentials within Metadynamics (MTD) simulations.
- Simultaneous sampling of orthogonal collective variables (CVs).
- Combined reweighting procedures using US and Tiwary-Parrinello MTD within the Weighted Histogram Analysis Method (WHAM).
- Application of ab initio and QM/MM hybrid molecular dynamics simulations.
Main Results:
- The combined MTD-US approach significantly improves computational efficiency for sampling flat, broad, and unbound free energy surfaces.
- Distributed sampling of high-dimensional free energy surfaces is achieved, further enhancing efficiency.
- A computationally affordable method for MTD bias reweighting to compute forward reaction barriers without requiring recrossing trajectories was proposed.
Conclusions:
- The hybrid MTD-US technique offers a powerful and efficient solution for sampling complex free energy landscapes.
- This method is ideal for studying chemical reactions and conformational changes in various systems.
- The approach provides a computationally tractable way to calculate reaction barriers in demanding simulations.
