Some recent results on assessing and developing density functionals

Density functionals are inexact in by design because that presents the possibility of achieving high efficiency and acceptable accuracy. Assessments of accuracy therefore play a crucial role in practical density functional theory. In this talk I will discuss three topics related to this general issue. The first is presenting a new database that we call the "Gold Standard Chemical Database 138" (GSCDB138), which is a substantial expansion and revision of the earlier "Main Group Chemical Database 84" (MGCDB84). In addition to revisions for accuracy, GSCDB138 includes a range of new chemically relevant energy differences that characterize the density, indirectly assess excited states, and directly probe key molecular properties. It also expands coverage of the periodic table to include an extensive range of energy differences in transition metal containing compounds. GSCDB138 assessments of leading hybrid functionals will be reported, and preliminary progress on the design of new functionals may be discussed. The second topic concerns best practices in functional benchmarking as applied to chemical kinetics, as a specific case study. I wish to emphasize the key importance of performing orbital stability analysis to find the lowest energy solution. The third topic concerns the smoothness of the widely used Grimme D3 and D4 dispersion corrections.