An efficient extrapolation to the (T)/CBS limit.

Area of Science:

• Quantum Chemistry
• Computational Chemistry
• Theoretical Chemistry

Background:

• Accurate prediction of molecular energies is crucial for chemical research.
• Extrapolation to the (T)/complete basis set (CBS) limit is a standard, yet computationally intensive, method.
• Development of efficient basis sets is needed to reduce computational cost.

Purpose of the Study:

• To introduce and validate new double-zeta (Wes1T-2Z) and triple-zeta (Wes1T-3Z) basis sets for extrapolating to the (T)/CBS limit.
• To assess the accuracy and cost-effectiveness of the new Wes1T-(2,3)Z extrapolation method.
• To provide a more efficient approach for calculating the (T) component in composite model chemistries.

Main Methods:

• Optimization of Wes1T-2Z and Wes1T-3Z basis sets for 102 chemical species across the first two rows of the Periodic Table.
• Extrapolation of perturbative triples (T) energies to the complete basis set (CBS) limit using the new basis sets.
• Comparison of Wes1T-(2,3)Z results with established benchmark (T)/CBS values and other model chemistries (W1, CBS-APNO, CBS-QB3).

Main Results:

• The extrapolated Wes1T-(2,3)Z triples energies show excellent agreement with (T)/CBS benchmarks (within ±0.65 mEh).
• The Wes1T-(2,3)Z method demonstrates significantly improved cost-effectiveness, with calculation times reduced by a factor of 25 compared to W1 for large systems.
• RMS deviations for Wes1T-(2,3)Z are competitive, with notable improvement over CBS-APNO and CBS-QB3.

Conclusions:

• The Wes1T-2Z and Wes1T-3Z basis sets provide a computationally efficient and accurate route for extrapolating to the (T)/CBS limit.
• The developed Wes1T-(2,3)Z extrapolation method is a valuable tool for theoretical chemistry, enabling more accessible high-accuracy energy calculations.
• These basis sets facilitate the efficient calculation of the (T) component in various composite model chemistries.