QMC Interaction energy calculation. We performed Fixed-Node Diffusion Monte Carlo (FN-DMC) calculations for QUID dimers in which there is a discrepancy between E int values at CCSD(T) and PBE0-MBD results, corroborating the correct E int with another accurate QM method. Our FN-DMC wave function ansatz was built using a single Slater determinant in addition to a Jastrow factor with one-body, two-body, and 3/4-body terms to account for cusps conditions at the nuclei, fermionic pair correlations, and product of pair correlations at the field of the nuclei, respectively. See references for further details about the electronic wave function ansatz. The molecular orbitals of the Slater determinant were taken from a previous DFT calculation employing ORCA code with the Local-density approximation (LDA) exchange-correlation functional, a cc-pVTZ basis set for all atoms, and the ccECP pseudopotential .