Correlation consistent basis sets for explicitly correlated wavefunctions: valence and core-valence basis sets for...

Area of Science:

• Computational chemistry
• Quantum chemistry
• Method development

Background:

• Explicitly correlated F12 methods offer significant computational advantages.
• Accurate basis sets are crucial for high-fidelity quantum chemical calculations.
• Basis sets for alkali and alkaline earth metals are needed for F12 methods.

Purpose of the Study:

• Optimize correlation consistent basis sets for alkali and alkaline earth metals (Li, Be, Na, Mg) for F12 methods.
• Develop auxiliary basis sets for resolution of the identity and density fitting approximations.
• Validate the accuracy of the new basis sets for various molecular properties.

Main Methods:

• Optimization of valence-only (cc-pVnZ-F12) and core-valence (cc-pCVnZ-F12) basis sets.
• Development of complementary auxiliary basis sets for resolution of the identity (RI) and density fitting (DF) approximations.
• Application of the approximate coupled cluster singles doubles and perturbative triples F12b (CCSD(T)-F12b) method on sixteen test molecules.

Main Results:

• New basis sets demonstrate high accuracy for optimized geometries, harmonic vibrational frequencies, and atomization energies.
• CCSD(T)-F12b calculations with triple-zeta quality basis sets achieve results comparable to conventional CCSD(T) quintuple-zeta.
• Outer core electron correlation effects on spectroscopic constants are accurately captured using cc-pCVDZ-F12 basis sets.

Conclusions:

• The developed basis sets are efficient and accurate for explicitly correlated F12 calculations on alkali and alkaline earth metals.
• These new basis sets significantly reduce the computational cost while maintaining high accuracy.
• The optimized sets enable more reliable predictions of molecular properties for these elements.