Extended combination rule for like-atom dipole dispersion coefficients.

Area of Science:

• Atomic and Molecular Physics
• Quantum Chemistry
• Computational Physics

Background:

• Accurate calculation of interatomic forces is crucial in physics and chemistry.
• Dipole-dipole dispersion coefficients (C6) are key parameters for describing long-range interactions.
• Existing methods for calculating C6 coefficients can be computationally intensive or limited in scope.

Purpose of the Study:

• To develop an extended combination rule for calculating dipole-dipole dispersion coefficients.
• To relate the dispersion coefficients of like target species interactions to those involving partner species.
• To assess the accuracy and applicability of the proposed combination rule.

Main Methods:

• Derivation of the combination rule via uniform discretization of the Casimir-Polder integral.
• Alternative derivation by relating dynamic dipole polarizabilities of target and partner species.
• Solving a system of linear equations requiring knowledge of partner species interaction coefficients.

Main Results:

• The proposed extended combination rule accurately predicts dipole-dipole dispersion coefficients.
• Tests show accuracy better than 1% for Ytterbium (Yb) atom interacting with rare gases and alkaline-earth metals.
• The rule provides a reliable method for calculating C6 coefficients between diverse atomic species.

Conclusions:

• The extended combination rule offers a highly accurate and efficient method for determining dipole-dipole dispersion coefficients.
• This approach simplifies the calculation of interatomic interaction parameters.
• While accurate for dispersion coefficients, the rule does not guarantee accurate dynamic polarizability approximations.