Self-interaction-free exchange-correlation functional for thermochemistry and kinetics

We develop a self-interaction-free exchange-correlation functional which is very accurate for thermochemistry and kinetics. This is achieved by theoretical construction of the functional form and nonlinear fitting. We define a simple interpolation of the adiabatic connection that uses exact exchange, generalized gradient approximation (GGA) and meta-GGA functionals. The performance is optimized by fitting a small number of empirical parameters. Overall the new functional improves significantly upon hybrids and meta-GGAs while correctly describing one-electron systems. The mean absolute error on a large set of reaction barriers is reduced to 1.99 kcal/mol.