Reducing the time-step errors in diffusion Monte Carlo

Area of Science:

• Computational Chemistry
• Quantum Monte Carlo Methods

Background:

• Diffusion Monte Carlo (DMC) is a powerful quantum mechanical simulation method.
• Time-step errors can affect the accuracy of DMC total energy calculations.
• Size-consistency is crucial for accurately describing weakly interacting systems.

Purpose of the Study:

• To reduce time-step errors in the total energy of systems calculated with DMC.
• To develop a size-consistent reweighting scheme for DMC.
• To improve the accuracy of binding energy calculations for weakly interacting systems.

Main Methods:

• Modification of the reweighting factor in the DMC projector.
• Development and implementation of an exactly size-consistent reweighting scheme.

Main Results:

• Reduced time-step error in total energy calculations.
• Achieved exact size-consistency in the reweighting scheme.
• Demonstrated reduction in time-step error for binding energies of weakly interacting systems.

Conclusions:

• The modified reweighting factor effectively reduces time-step errors in DMC.
• The new reweighting scheme ensures accurate energy calculations for fragmented systems.
• This work enhances the reliability of DMC for studying weakly bound molecular systems.