Reaching a Uniform Accuracy for Complex Molecular Systems: Long-Range-Corrected XYG3 Doubly Hybrid Density Functional

An unbiased understanding of complex molecular systems from first-principles critically demands theoretical methods with uniform accuracy for diverse interactions with different natures covering short-, medium-, and long-range correlations. Among the state-of-the-art density functional approximations (DFAs), doubly hybrid (DH) DFAs (e.g., XYG3 in this Letter) provide a remarkable improvement over the conventional DFAs (e.g., B3LYP in this Letter). Even though XYG3 works quite well in many cases of noncovalent bonding interactions (NCIs), it is incomplete in describing the pure long-range dispersive interactions. Here, we address such concerns by adding a scaled long-range contribution from the second-order perturbation theory (PT2). The long-range-corrected XYG3 (lrc-XYG3) is proposed without reparameterizing the three parameters in the original XYG3. Due to its overall excellent performance for all testing sets constructed for various purposes, lrc-XYG3 is the recommended method, which is expected to provide a balanced description of diverse interactions in complex molecular systems.