Assessing weak hydrogen binding on Ca+ centers: an accurate many-body study with large basis sets

Area of Science:

• Computational chemistry
• Quantum mechanics
• Materials science

Background:

• Accurately calculating weak hydrogen molecule (H2) physisorption energies is a significant challenge for theoretical methods.
• The Ca(+)-4H(2) system is a key model for testing electronic structure methods for H2 binding on alkaline earth metals.

Purpose of the Study:

• To accurately predict the binding energy of Ca(+)-4H(2) using the phaseless auxiliary-field quantum Monte Carlo method.
• To assess the reliability of advanced computational methods for describing H2 binding interactions.

Main Methods:

• Utilized the phaseless auxiliary-field quantum Monte Carlo (AFQMC) method.
• Implemented a modified Cholesky decomposition for efficient Hubbard-Stratonovich transformation.
• Employed large, correlation-consistent Gaussian basis sets (up to cc-pCV5Z for Ca) and extrapolated to the complete basis set limit.

Main Results:

• Successfully predicted the binding energy of Ca(+)-4H(2).
• The calculated potential energy curve demonstrated a binding interaction.
• A distinct double-well structure was observed in the potential energy curve.

Conclusions:

• The phaseless AFQMC method provides accurate binding energies for challenging H2 physisorption systems.
• The Ca(+)-4H(2) system exhibits a double-well binding potential, confirming its utility as a benchmark.
• Advanced computational techniques are crucial for understanding weak interactions in materials science.