Spin-component scaled coupled-clusters singles and doubles optimized towards calculation of noncovalent interactions

Area of Science:

• Computational chemistry
• Quantum chemistry
• Molecular interactions

Background:

• Accurate calculation of molecular interaction energies is crucial for understanding noncovalent interactions.
• Coupled cluster methods like CCSD(T)/CBS offer high accuracy but are computationally expensive.
• Previous scaling methods (SCS-CCSD) showed promise but had limitations.

Purpose of the Study:

• To reparametrize the scaling parameters for the SCS-CCSD method.
• To develop a more accurate and computationally feasible method for calculating interaction energies.
• To improve the accuracy of noncovalent interaction energy calculations.

Main Methods:

• Reparametrization of same- and opposite-spin scaling parameters for SCS-CCSD.
• Utilizing benchmark CCSD(T)/Full-configuration interaction singles and doubles with a complete basis set (CCSD(T)/CBS) interaction energies from the S22 set.
• Testing the new method on the S22 and S22x5 datasets, including non-equilibrium geometries.

Main Results:

• New parameters for SCS(MI)-CCSD are 1.11 (opposite-spin) and 1.28 (same-spin).
• Significantly reduced Root Mean Square Deviation (RMSD) and largest error for the S22 set compared to original parametrization.
• Slightly increased statistical errors on the S22x5 set (including non-equilibrium geometries) compared to S22.

Conclusions:

• The new SCS(MI)-CCSD method provides highly accurate interaction energy calculations.
• It is recommended for diverse noncovalent interaction types where CCSD(T)/CBS is impractical.
• This method offers a computationally efficient alternative for accurate molecular interaction studies.