Non-orthogonal determinants in multi-Slater-Jastrow trial wave functions for fixed-node diffusion Monte Carlo

Area of Science:

• Computational Chemistry
• Quantum Mechanics
• Materials Science

Background:

• Accurate Quantum Monte Carlo (QMC) calculations rely on effective variational trial wave functions.
• Compact wave functions are crucial for improving the efficiency and accuracy of ab initio QMC methods.

Purpose of the Study:

• To investigate the use of multi-Slater-Jastrow trial wave functions with non-orthogonal determinants.
• To assess the impact of optimizing identical single-particle orbitals independently within separate determinants.

Main Methods:

• Employed variational and fixed-node diffusion Monte Carlo (FN-DMC) methods.
• Utilized a C2 molecule as a test case for calculations.
• Optimized non-orthogonal determinants within multi-Slater-Jastrow wave functions.

Main Results:

• Non-orthogonal determinant optimization consistently improved variational and FN-DMC energies by tenths of an eV.
• Achieved comparable or better accuracy in FN-DMC with fewer non-orthogonal determinants than orthogonal ones.
• Demonstrated enhanced energy computations using non-orthogonal determinants compared to orthogonal counterparts.

Conclusions:

• Trial wave functions incorporating non-orthogonal determinants offer a significant advantage in QMC calculations.
• This approach leads to more accurate and potentially more efficient electronic structure computations.
• The findings suggest a promising avenue for advancing ab initio QMC methodologies.