LNO-CCSD(T) reference interaction energies. The large CCSD(T) computations well beyond the limits of conventional implementations were performed with the highly optimized local natural orbital (LNO) CCSD(T) method in the MRCC quantum chemistry suite. First, a detailed basis set and LNO approximation convergence study is performed to determine the most efficient LNO and basis set settings that provide high accuracy for the interactions relevant to QUID. To that end, the interaction energies were tested for three representative dimers, namely SF2I2 (Fig. ), F2B1, and L2B3 (Fig. of the SI), at 1×, 0.9×, and 2.0× equilibrium distances. Here, we used the systematically improving series of aug-cc-pV(X+d)Z basis sets with X = D, T and Q as well as Normal (N), Tight (T), and very Tight (vT) LNO thresholds. The convergence toward the complete basis set (CBS) limit was accelerated for the HF and correlation 87 energies via CBS extrapolation [CBS(X,X + 1)]. To accelerate the convergence toward conventional CCSD(T), that is the local approximation free (LAF) limit, the LAF extrapolations Our best estimate of CCSD(T)/CBS for the above nine dimers is given by a composite ( Ē) scheme benefiting from CBS(T,Q) and LAF T-vT extrapolations as well as counterpoise corrections :