A General Accuracy Ladder for Molecular Structures: From Bonds to Interaction-Driven, Transferable Building Blocks.

Area of Science:

• Computational chemistry
• Quantum chemistry
• Molecular modeling

Background:

• Accurate structural interpretation is vital but challenging for systems with nonlocal effects.
• Standard density functional methods struggle with delocalized open-shell and hydrogen-bonded systems due to inappropriate error scales.

Purpose of the Study:

• To develop a new approach for accurate structural predictions in complex molecular systems.
• To establish a direct link between error origin scale and computational theory level.

Main Methods:

• Formulating transferable corrections based on interaction-driven building blocks instead of individual bonds.
• Automatically identifying and assigning these blocks to an accuracy ladder.
• Consistent treatment of vibrational averaging.

Main Results:

• Quantitative agreement with experimental data for radicals, nonplanar aromatics, and hydrogen-bonded networks.
• Reproducing experimental rotational constants within 0.1-0.2%.
• Achieving root-mean-square atomic position deviations of 1-2 × 10^-3 Å.

Conclusions:

• Matching the scale of error transferability with the appropriate level of electronic structure theory is key for accurate structures.
• Multilevel computational strategies are effective for large systems with varying complexity.
• This approach provides accurate structural predictions at an affordable computational cost.