On the relationship between bond-length alternation and many-electron self-interaction error.

Area of Science:

• Computational chemistry
• Theoretical chemistry
• Materials science

Background:

• Predicting bond-length alternations (BLAs) in long conjugated molecular chains presents a long-standing challenge for electronic-structure theory.
• Hartree-Fock (HF) methods tend to overestimate BLAs, while second-order perturbation theory and common density functional theory (DFT) approaches typically underestimate them.

Purpose of the Study:

• To investigate the role of many-electron self-interaction error (MSIE) in the inaccurate prediction of BLAs.
• To explore the effectiveness of tuned long-range corrected hybrids in addressing MSIE and improving BLA predictions for polyenes.

Main Methods:

• Utilized tuned long-range corrected hybrid functionals to systematically minimize MSIE in polyene chains.
• Analyzed the relationship between MSIE minimization and the accuracy of predicted BLAs.
• Investigated the impact of tuning the range-separation parameter on both MSIE and BLA accuracy.

Main Results:

• Minimizing MSIE alone was insufficient to achieve accurate BLAs in the studied polyenes.
• Tuning the range-separation parameter to obtain accurate BLAs resulted in a significant MSIE that increased with chain length.
• A trade-off exists between MSIE reduction and BLA accuracy in DFT calculations.

Conclusions:

• The accurate prediction of BLAs in conjugated systems requires more than just the minimization of MSIE.
• Density functional theory approaches need further development to simultaneously address MSIE and achieve reliable BLA predictions for extended molecular systems.