1. There are still a few die-hards in condensed matter that prefer LDA, which gets the lattice constant of bulk silicon almost exactly right. Even PBEsol did not beat that.
2. Don Hamann is an extremely distinguished solid-state theorist who spent much of his career at Bell Labs. He mentioned that it took him 2 weeks of hard work in the library at the Aspen Center for Physics to find and read all the bits of the PW91 derivation, scattered as they were over many papers and years. In summer 2001, he also pointed out to us that PBE gets the ground-state energy of the hydrogen atom right to about 4 digits and wondered if we had done some surreptitious fitting. This was news to us and either just dumb luck or some fundamental consistency in the universe.
3. Of course all good chemists know that PBE is woefully inadequate for many dissociation energies and that you really need a hybrid, such as PBE0, a.k.a. PBE1PBE.
4. Another bonus that came with being at Tulane was the chance to interact and collaborate with Mel Levy who was in the chemistry department. He famously wrote in his research proposal when he applied for a faculty position there that he would find the exact XC functional (which, in a sense, he did with his constrained search approach). This was a brilliant move, as he spent his entire career at Tulane working on that original proposal, and he is still not finished!
5. This was when Hardy Gross (a.k.a. E.K.U.) first asked me about how to calculate conductances through single molecules, a project he and I have happily worked away at for a decade now. Hmm, sounds quite like Mel’s original proposal.