Accurate and Cost‐Efficient <scp>DLPNO</scp>‐<scp>CCSD</scp>(T)‐Based Feller‐Peterson‐Dixon Protocols Calibrated on Association Reactions of Li⁺ Ion With Mixed Organic Carbonates

We present a benchmark set LIMIXCARB_RE12 comprising 12 reference DLPNO-CCSD(T₁)/CPS(6,7)/CBS(cc-pwCVTZ/cc-pwCVQZ)//PBE0-D3(BJ)/def2-TZVP binding energies for the sizeable (up to 69 atoms) clusters of Li⁺ ion with mixed cyclic and linear organic carbonates. A number of computationally cheaper DLPNO-CCSD(T)-based Feller-Peterson-Dixon protocols including contributions due to core-valence electron correlation, using more accurate iterative triples correction (T₁) and tighter-than-default PNO settings are examined with respect to their accuracy and efficiency. Particular splittings of the total binding energy into components allow maintaining high accuracy (deviations less than 0.2 kcal mol^-1) at significantly reduced computational cost. Much faster convergence of the DLPNO-CCSD(T) binding energies to the reference values is reached if Ahlrichs' def2 basis sets are used instead of their correlation-consistent Dunning counterparts. Evaluation of the DFT approximations against the LIMIXCARB_RE12 reveals double hybrid PWPB95-D4 in conjunction with CBS(def2-TZVPP/def2-QZVPP) extrapolation to be the best performer with mean signed deviation (MSD) of only -0.1 kcal mol^-1 followed by r²SCAN-D4/D3(BJ) and r²SCAN-3c (MSD < 1 kcal mol^-1), while hybrid B3LYP and PBE0 functionals complemented with D3(BJ) or D4 dispersion corrections are clearly inferior. The obtained results provide a guide for the accurate calculations of the binding energies of the microsolvated clusters and can be used for the development and validation of the emerging computational methods.