LAUSR

In the present study, we have investigated the performance of RIJCOSX DLPNO‐CCSD(T)‐F12 methods for a wide range of systems. Calculations with a high‐accuracy option [“DefGrid3 RIJCOSX DLPNO‐CCSD(T1)‐F12”] extrapolated to the complete‐basis‐set limit using the maug‐cc‐pV[D+d,T+d]Z basis sets provides fairly good agreements with the canonical CCSD(T)/CBS reference for a diverse set of thermochemical and kinetic properties [with mean absolute deviations (MADs) of ~1–2 kJ mol−1 except for atomization energies]. On the other hand, the low‐cost “RIJCOSX DLPNO‐CCSD(T)‐F12D” option leads to substantial deviations for certain properties, notably atomization energies (MADs of up to tens of kJ mol−1). With the high‐accuracy CBS approach, we have formulated the L‐W1X method, which further includes a low‐cost core–valence plus scalar‐relativistic term. It shows generally good accuracy. For improved accuracies in specific cases, we advise replacing maug‐cc‐pV(n+d)Z with jun‐cc‐pV(n+d)Z for the calculation of electron affinities, and using well‐constructed isodesmic‐type reactions to obtain atomization energies. For medium‐sized systems, DefGrid3 RIJCOSX DLPNO‐CCSD(T1)‐F12 calculations are several times faster than the corresponding canonical computation; the use of the local approximations (RIJCOSX and DLPNO) leads to a better scaling than that for the canonical calculation (from ~6–7 down to ~2–4 for our test systems). Thus, the DefGrid3 RIJCOSX DLPNO‐CCSD(T1)‐F12 method, and the L‐W1X protocol that based on it, represent a useful means for obtaining accurate thermochemical quantities for larger systems.