Optimizing Jastrow factors for the transcorrelated method.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• The transcorrelated (TC) method offers a pathway to high accuracy in quantum chemistry.
• Optimizing Jastrow factors is crucial for the efficiency and accuracy of the TC method.
• Accurate calculation of molecular properties requires robust computational methods.

Purpose of the Study:

• To optimize flexible real-space Jastrow factors for the transcorrelated (TC) method.
• To evaluate the performance of TC method with optimized Jastrow factors in combination with initiator full configuration interaction quantum Monte Carlo (FCIQMC).
• To assess the impact of neglecting three-body excitations on TC-FCIQMC calculations.

Main Methods:

• Optimization of Jastrow factors by minimizing the variance of the TC reference energy.
• Calculation of all-electron atomization energies for first-row molecules (C2, CN, N2, O2).
• Implementation and testing of an approximation neglecting pure three-body excitations in TC-FCIQMC dynamics.

Main Results:

• Minimizing variance of TC reference energy yields superior Jastrow factors compared to minimizing variational energy.
• The TC method with optimized Jastrow factors achieves chemical accuracy for atomization energies using the cc-pVTZ basis set.
• Neglecting three-body excitations in TC-FCIQMC dynamics has a negligible impact on relative energies.
• Results demonstrate accuracy comparable to larger basis sets without TC.

Conclusions:

• Tailored real-space Jastrow factors combined with multi-configurational TC-FCIQMC provide a route to chemical accuracy.
• This approach enables accurate calculations with modest basis sets, avoiding basis-set extrapolation and composite techniques.
• The TC method offers a computationally efficient path to high-accuracy quantum chemical results.