Binding Energy Calculations of Anthracene and Rhodamine 6G H-Type Dimers: A Comparative Study of DFT and SMD Methods

With the ever-growing need to study systems of increased size and complexity, modern density functional theory (DFT) methods often encounter problems arising from the growing computational demands. In this work, we have presented a comprehensive DFT validation of the steered molecular dynamics (SMD) approach in estimating the binding energies of aromatic dimers. By performing DFT calculations on optimized and unoptimized anthracene and rhodamine 6G (R6G) dimers using functionals with progressively enhanced exchange-correlation energy description and comparing the obtained results with SMD-predicted values, it was found that SMD predictions are in good agreement with the results obtained from hybrid DFT calculations. The average binding energies for optimized anthracene dimers were found to be 6.46 kcal/mol using DFT at ωB97X-D4/def2-QZVPP and 7.64 ± 1.61 kcal/mol as predicted by the SMD. For the R6G H-type dimer, the binding energies were 17.48 and 19.02 ± 2.22 kcal/mol, respectively. The study also revealed that due to the lack of explicit terms accounting for electron-electron interactions in MD force fields, the proposed method tends to overbind dimers. It is anticipated that the presented method can be applied to more complex dimers, potentially accelerating the calculations of binding energies. Moreover, this study further validates the accuracy of the CHARMM36 FF.