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Long range intermolecular interactions between the alkali diatomics Na(2), K(2), and NaK
Warren T Zemke1, Jason N Byrd, H Harvey Michels
1Department of Chemistry, Wartburg College, Waverly, Iowa 50677, USA.
The Journal of Chemical Physics
|July 2, 2010
Summary
This study investigates long-range interactions between alkali diatomic molecules like Na2 and K2. A new asymptotic model accurately predicts these intermolecular forces using molecular properties.
Area of Science:
- Physical Chemistry
- Quantum Chemistry
- Molecular Interactions
Background:
- Understanding intermolecular forces is crucial in physical chemistry.
- Alkali diatomics exhibit unique electronic properties influencing their interactions.
Purpose of the Study:
- To examine long-range interactions between ground-state alkali diatomics: Na2-Na2, K2-K2, Na2-K2, and NaK-NaK.
- To compare ab initio calculated interaction energies with a simplified asymptotic model.
Main Methods:
- Ab initio calculations using coupled-cluster with singles, doubles, and perturbative triples [CCSD(T)] level of theory.
- Inclusion of counterpoise corrections to account for basis set superposition error.
- Calculation of long-range energies using diatomic molecular properties: polarizabilities, dipole, and quadrupole moments.
Main Results:
- Ab initio calculations provided accurate interaction energies for the alkali diatomic systems.
- The asymptotic model, E(LR)=E(elec)+E(disp)+E(ind), effectively reproduced the ab initio interaction energies at long range.
- Molecular properties like polarizabilities and moments were key inputs for the model.
Conclusions:
- A simple asymptotic model can accurately describe long-range intermolecular interactions for alkali diatomics.
- This model offers a computationally efficient alternative to complex ab initio methods for predicting these interactions.
- The findings are relevant for understanding van der Waals forces in alkali systems.
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