How accurate is the density functional theory combined with symmetry-adapted perturbation theory approach for CH-π and π-π interactions? A comparison to supermolecular calculations for the acetylene-benzene dimer.
Five different orientations of the acetylene-benzene dimer including the T-shaped global min. structure are used to assess the accuracy of the d. functional theory combined with symmetry adapted perturbation theory (DFT-SAPT) approach in its d.-fitting implementation (DF-DFT-SAPT) for the study of CH-π and π-π interactions. The results are compared with the outcome of counterpoise cor. supermol. calcns. employing second-order Moller-Plesset (MP2), spin-component scaled MP2 (SCS-MP2) and single and double excitation coupled cluster theory including perturbative triple excitations (CCSD(T)). For all considered orientations MP2 predicts much deeper potential energy curves with considerably shifted min. compared to CCSD(T) and DFT-SAPT. In spite of being an improvement over the results of MP2, SCS-MP2 tends to underestimate the well depth while DFT-SAPT, employing an asymptotically cor. hybrid exchange-correlation potential in conjunction with the adiabatic local d. approxn. for the exchange-correlation kernel, is found to be in excellent agreement with CCSD(T). Furthermore, DFT-SAPT provides a detailed understanding of the importance of the electrostatic, induction and dispersion contributions to the total interaction energy and their repulsive exchange corrections.
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