Non-empirical quadratic-integrand double-hybrid (QIDH) functionals

Robust and universally applicable double-hybrid functionals are developed in the last decade for all kinds of electronic structure calculations. The expressions presented here are based on the adiabatic connection model introducing a proper interpolation (quadratic) function and are free of any empirical parameterization. We have also developed extensions to adequately incorporate long-range exchange and (non-covalent) correlation effects, as well as efficient techniques to allow the application of these expressions to considerably large systems. Additionally, the corresponding linear-response time-dependent formalism can also be applied to deal with excited-states calculations. The systematic benchmarking of these models along the years have proved their accuracy on a wide range of chemical systems and properties of the most interest. Thus, they represent a set of useful tools for electronic structure calculations which, furthermore, are widely available in many computational chemistry codes.