Benzenium-ethene complex: a fundamental problem for standard second-order Møller-Plesset theory

Area of Science:

• Computational chemistry
• Quantum mechanics
• Chemical reaction theory

Background:

• Second-order Møller-Plesset perturbation theory (MP2) has shown inaccuracies in predicting reaction barriers, specifically for the benzenium-ethene complex.
• Previous studies suggested basis set superposition error as the cause for MP2's failure.

Discussion:

• This study refutes the basis set superposition error hypothesis.
• The failure of MP2 is attributed to an intrinsic overcorrelation problem inherent in the method.
• Analysis reveals that MP2's correlation treatment is inadequate for this specific reaction system.

Key Insights:

• MP2's overcorrelation issue leads to incorrect prediction of a barrierless reaction pathway.
• SCS-MP2 and B2PLYP double-hybrid functionals accurately predict the reaction barrier.
• Accurate quantum chemical methods are crucial for reliable chemical reaction modeling.

Outlook:

• Further investigation into the overcorrelation problem in perturbation theory is warranted.
• Development of more robust and accurate quantum chemical methods is essential for complex reaction studies.
• Application of validated methods to other challenging reaction systems in computational chemistry.