DLPNO-CCSD(T) for basis set convergence

[haneug]

It would be nice to include DLPNO-CCSD(T) for the basis set convergence task as DLPNO methods become more and more relevant and feasible. Maybe we could pick a converged reference value from a benchmark and let the students try to reach it with DLPNO-CCSD(T) and DFT. We could also add a really small basis set to show how correlated methods perform with an insufficient basis set, which is not sufficiently shown with the current task.

[maburs]

Just a comment: Maybe one should also include a PNO threshold convergence task. DLPNO-CCSD(T) is quite special and maybe worth an own task in general?