Prospects for release-node quantum Monte Carlo.

Area of Science:

• Computational Quantum Chemistry
• Quantum Monte Carlo Methods
• Molecular Electronic Structure

Background:

• Accurate calculation of ground-state energies is crucial for understanding molecular properties.
• Quantum Monte Carlo (QMC) methods offer a powerful approach for electronic structure calculations.
• The release-node QMC method is a variant designed to improve computational efficiency.

Purpose of the Study:

• To assess the accuracy of release-node quantum Monte Carlo simulations for first-row diatomic molecules.
• To investigate the dependence of simulation accuracy on nuclear charge (Z).
• To determine the feasibility of extrapolating to exact ground-state energies using this method.

Main Methods:

• Performed release-node quantum Monte Carlo simulations on first-row diatomic molecules.
• Analyzed the fermion-boson energy difference and its relation to nuclear charge.
• Utilized maximum entropy analysis for energy extrapolation.

Main Results:

• The fermion-boson energy difference and variance growth are strongly dependent on nuclear charge (Z).
• Accurate extrapolation to ground-state energies was only possible for low Z elements (Li2, Be2, B2).
• For higher Z elements, excessive error growth prevented accurate calculations at long imaginary times.

Conclusions:

• Release-node QMC is accurate for low Z first-row diatomics, yielding ground-state energies for Li2, Be2, and B2.
• The method's accuracy is limited for higher Z elements due to rapid error accumulation.
• Further methodological development is needed to extend accurate QMC simulations to heavier diatomics.