Nonlocal pseudopotentials and time-step errors in diffusion Monte Carlo

Area of Science:

• Computational Physics
• Quantum Chemistry

Background:

• Diffusion Monte Carlo (DMC) is a powerful quantum mechanical simulation method.
• Accurate treatment of nonlocal pseudopotentials is crucial for efficiency and accuracy in DMC.
• Existing T-moves approaches in DMC have limitations regarding time-step errors.

Purpose of the Study:

• To develop an improved T-moves approach for treating nonlocal pseudopotentials in DMC.
• To reduce time-step errors in DMC simulations.
• To maintain the desirable upper-bound property for energy calculations.

Main Methods:

• A modified version of the T-moves approach was developed for nonlocal pseudopotentials.
• The reweighting factor of the projector in DMC was modified.
• The new approach was applied to diffusion Monte Carlo simulations.

Main Results:

• The new T-moves approach exhibits significantly smaller time-step errors compared to existing methods.
• The upper-bound property for energy is preserved.
• Modifications to the reweighting factor effectively reduce time-step errors in both pseudopotential and all-electron calculations.

Conclusions:

• The presented T-moves approach offers a more accurate and efficient method for DMC simulations involving nonlocal pseudopotentials.
• The modifications enhance the reliability of DMC results by minimizing time-step dependence.
• The developed techniques are broadly applicable, benefiting both pseudopotential and all-electron DMC calculations.