Abstract: In this talk, the adiabatic connection (AC) formalism, coordinate scaling relations, and the second orderG?rling-Levy perturbation theory(GL2) are first reviewed. Emphasis is laid upon the construction of the AC integrand ( ), with suitable input data and the proper asymptotic behavior on as . This leads to a non-empirical DH functional, namely PBE-ACDH.The PBE-ACDH functional is unique in that it explicitly considers contributions from density scaling and singles, and it utilizes density and orbital information from the PBE functional, which has a local multiplicative potential, being most compatible with the GL2 theory. Systematical tests on heats of formation, bond dissociation enthalpies, reaction barrier heights and nonbonded interactions, using some well-established benchmarking sets, suggest that PBE-ACDH is a significant improvement over its parent functional PBE, as well as PBE0, Beckes Half-and-Half (PBE-HH) and GL2. The physical insight gained in the present work should prove useful for the further development of newfunctionals.