Implement relPBE0 functional
Described in J. Chem. Phys. 155, 161103 (2021).
The functional is very simple:
The implemented SHapley Additive exPlanations (SHAP) analysis (i.e., a tool to determine a signed impact of inner parameters to a target value27) revealed a strict correlation between the increasing accuracy and decreasing mue value. The optimal value appeared to be 0.041 02 instead of original 0.219 52. The percentage of HF exchange remained quite similar to the original (23% vs 25%) as well as alpha and beta parameters (0.670 28 vs 0.666 67 and 0.067 912 vs 0.066 725, respectively). The small increase in the kappa parameter (1.009 vs 0.804) was earlier proved to increase energy accuracy by the developers of the revPBE functional28 (the corresponding value there was 1.245).
mu
and kappa
are the parameters in PBE exchange, while beta
is a parameter in PBE correlation.
The only issue is that it is not obvious what the authors mean by the alpha
parameter.