and that strategy is adopted in both the Xi et al. study and the present one. One parameter is involved in two-point extrapolation of 𝐸 !" , and another parameter is involved in two-point extrapolation of 𝐸 #$%% ; the former is called a, and the latter is called b. Xi et al. examined five formulas for two-point extrapolation of 𝐸 !" , and five formulas for two-point extrapolation of 𝐸 #$% , they found that, as long as a and b were separately optimized for each formula and each pair of basis sets [D,T or T,Q or Q,5], the results showed similar high accuracy all five formulas for HF extrapolation and similar high accuracy all five formulas for correlation-energy extrapolation. We therefore chose to use only one formula in each case, and we chose the model that they named Truhlar-1998 Error! Bookmark not defined. for both cases.