Comparison of Standard Functionals to Calculate the Properties of Molecules at the Variational Limit

Abstract

B1LYP, B1PW91, B3LYP, BHandH, BHandHLYP, BLYP, BP, CAMY-B3LYP, HTBS, KMLYP, LCYBLYP, LCY-BP86, LCY-PBE, LDA, M06, M06-2X, M06-HF, M06L, mPBE, mPW, MPW1K, MPW1PW, O3LYP, OLYP, OPBE, OPBE0, PBE, PBE0, PBEsol, PW91, revPBE, revTPSS, RPBE, TPSS, TPSSH, X3LYP, and HF methods are used to calculate the electron energy Eel of the reference GeO and C2H6 compounds in Slater basis sets QZ4P, aug-TZ2P, and TZ2P, as well as DZ for C2H6. The Eel values are recalculated into the bond breaking enthalpy D0(Ge–O) and formation enthalpy ΔfH2980 of ethane, and calculation errors for Eel are obtained at the variation limit. The ADF program settings are chosen so that they make it possible to attribute these Eel errors to the structure of DFT functionals. The dependence of the Eel values on the type (size) of the basis set is studied. It is demonstrated that when Eel is calculated for GeO, the optimum combination is DFT/TZ2P, where DFT = LCY-BLYP, LCY-BP86, LCY-PBE, CAMYB3LYP; for C2H6 it is DFT/TZ2P, where DFT = PBE0, M06, mPBE, OLYP. Errors in the calculation of the geometric parameters are studied.