Relativistic correction to the helium dimer interaction energy

Area of Science:

• Quantum Chemistry
• Atomic Physics
• Intermolecular Forces

Background:

• Accurate calculation of interaction energies is crucial for understanding atomic and molecular systems.
• Relativistic effects become significant for precise energy calculations, even in light systems like helium.
• Previous calculations lacked the lowest-order relativistic correction for helium-helium interactions.

Purpose of the Study:

• To compute the lowest-order relativistic correction to the helium-helium interaction energy for the first time.
• To establish a new upper bound for the nonrelativistic Born-Oppenheimer interaction energy.
• To validate computational methods for relativistic corrections in atomic interactions.

Main Methods:

• Utilized two independent methods employing expansions in explicitly correlated Gaussian functions.
• Calculated relativistic corrections at the equilibrium interatomic distance of helium (5.6 bohr).
• Determined a new upper bound for the nonrelativistic Born-Oppenheimer interaction energy.

Main Results:

• The lowest-order relativistic correction was determined to be +15.4 +/- 0.6 mK.
• This represents the first calculation of this specific relativistic correction for helium-helium interactions.
• A new upper bound of -10.9985 K for the nonrelativistic Born-Oppenheimer interaction energy was obtained.

Conclusions:

• The calculated relativistic correction refines the understanding of helium-helium interactions.
• The study demonstrates the efficacy of explicitly correlated Gaussian functions for relativistic quantum calculations.
• The improved interaction energy provides a more accurate benchmark for theoretical and experimental studies.