Long-range interactions between like homonuclear alkali metal diatoms

Area of Science:

• Quantum Chemistry
• Computational Physics
• Spectroscopy

Background:

• Accurate calculation of interatomic potentials is crucial for understanding molecular interactions.
• Long-range forces significantly influence the behavior of alkali dimers.

Purpose of the Study:

• To compute long-range electrostatic and van der Waals coefficients for alkali dimers (Li2 to Cs2).
• To assess the accuracy of various density functionals and basis sets for these calculations.
• To investigate the applicability of the method to larger alkali clusters.

Main Methods:

• Sum over states (SOS) method.
• Ab initio and time-dependent density functional theory (TD-DFT).
• Calculation of static electric moments and polarizabilities up to octopole order.

Main Results:

• Evaluated electrostatic and van der Waals coefficients up to R(-8) for Li2-K2, with new results for Rb2 and Cs2.
• Calculated interaction potential curves show good agreement with high-level ab initio theory.
• Preliminary results indicate the method's suitability for larger alkali clusters.

Conclusions:

• The employed computational methods provide accurate long-range interaction coefficients for alkali dimers.
• The study validates the use of TD-DFT and SOS for predicting alkali dimer properties.
• The approach is extendable to more complex alkali systems, paving the way for further research.