Improving the accuracy of the nonlocal van der Waals density functionalwith minimal empiricism

摘要

The nonlocal van der Waals density functional (vdW-DF) captures the essential physics of thedispersion interaction not only in the asymptotic regime but also for a general case of overlappingfragment densities. A balanced treatment of other energetic contributions, such as exchange, iscrucial if we aim for accurate description of various properties of weakly bound systems. In thispaper, the vdW-DF correlation functional is modified to make it better compatible with accurateexchange functionals. We suggest a slightly simplified construction of the nonlocal correlation,yielding more accurate asymptotic C6 coefficients. We also derive a gradient correction, containinga parameter that can be adjusted to suit an exchange functional of choice. We devise a particularlyapt combination of exchange and correlation terms, which satisfies many important constraints andperforms well for our benchmark tests.