Coupled-cluster based basis sets for valence correlation calculations.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Accurate description of electron correlation is crucial in quantum chemistry.
• Existing basis sets like cc-pVXZ have limitations in describing valence correlation.
• The virial theorem provides a fundamental constraint for accurate electronic structure calculations.

Purpose of the Study:

• To develop novel basis sets (ANO-VT-XZ) for improved valence correlation.
• To ensure basis sets satisfy the virial theorem.
• To assess the performance of the new basis sets against established ones.

Main Methods:

• Generation of basis sets using the Atomic Natural Orbital (ANO) procedure.
• Utilizing CCSD(T) density matrices from Dunning's primitive functions.
• Uniform scaling of Gaussian function exponents to satisfy the virial theorem.
• Evaluation of contraction errors in atomic and molecular calculations.

Main Results:

• ANO-VT-XZ basis sets were created with the same number of contracted functions as cc-pVXZ.
• Energy calculations with ANO-VT-QZ achieved "chemical accuracy" (1 kcal/mol).
• ANO-VT-QZ demonstrated improved accuracy over cc-pVQZ in energy calculations.

Conclusions:

• The new ANO-VT-XZ basis sets offer enhanced accuracy for valence correlation.
• These basis sets represent an improvement over the cc-pVXZ series.
• ANO-VT-XZ basis sets are valuable for accurate quantum chemical computations.