Suppressing Ionic Terms with Number-Counting Jastrow Factors in Real Space.

Area of Science:

• Quantum Chemistry
• Computational Physics

Background:

• Accurate electronic structure calculations are crucial for understanding chemical phenomena.
• Strongly correlated systems pose significant challenges for traditional computational methods.
• Ionic terms in wave functions can lead to qualitatively incorrect results, especially in nodal surface descriptions.

Purpose of the Study:

• To introduce and validate a novel wave function stenciling technique using four-body real-space Jastrow factors.
• To improve the size consistency of wave functions.
• To enable the use of accurate nodal surfaces in diffusion Monte Carlo calculations for strongly correlated systems.

Main Methods:

• Development of four-body real-space Jastrow factors with appropriate basis functions.
• Application of wave function stenciling to remove unwanted ionic terms from an overabundant fermionic reference.
• Integration of the stenciling method with diffusion Monte Carlo.
• Testing the approach on a double bond dissociation to extract nodal surfaces.

Main Results:

• Successful removal of ionic terms without significantly altering other wave function components.
• Exact restoration of size consistency for geminal powers.
• Demonstrated compatibility of real-space stenciling with diffusion Monte Carlo.
• Extraction of a qualitatively correct nodal surface for a double bond dissociation, even with a restricted Slater determinant.

Conclusions:

• Four-body real-space Jastrow factors provide an effective method for wave function stenciling.
• This technique enhances the reliability of nodal surfaces in quantum chemical calculations.
• The approach offers a pathway to more accurate and compact trial functions for strongly correlated systems.