Treating London-Dispersion Effects with the Latest Minnesota Density Functionals: Problems and Possible Solutions.

It is shown that the latest Minnesota density functionals (SOGGA11, M11-L, N12, MN12-L, SOGGA11-X, M11, N12-SX, and MN12-SX) do not properly describe London-dispersion interactions. Grimme's DFT-D3 correction can solve this problem partially; however, double-counting of medium-range electron correlation can occur. For the related M06-L functional, the alternative VV10 van der Waals kernel is tested, but it experiences similar double-counting. Most functionals give unphysical dissociation curves for the argon dimer, an indication for method-inherent problems, and further investigation is recommended. These results are further evidence that the London-dispersion problem in density functional theory approximations is unlikely to be solved by mere empirical optimization of functional parameters, unless the functionals contain components that ensure the correct asymptotic long-range behavior. London dispersion is ubiquitous, which is why the reported findings are not only important for theoreticians but also a reminder to the general chemist to carefully consider their choice of method before undertaking computational studies.