Communication: Rationale for a new class of double-hybrid approximations in density-functional theory

We provide a rationale for a new class of double-hybrid approximations introduced by Brémond and Adamo [J. Chem. Phys. 135, 024106 (2011)10.1063/1.3604569 which combine an exchange-correlation density functional with Hartree-Fock exchange weighted by and second-order Mller-Plesset (MP2) correlation weighted by ³. We show that this double-hybrid model can be understood in the context of the density-scaled double-hybrid model proposed by Sharkas [J. Chem. Phys. 134, 064113 (2011)10.1063/1.3544215, as approximating the density-scaled correlation functional E_c[n₁ by a linear function of , interpolating between MP2 at 0 and a density-functional approximation at 1. Numerical results obtained with the Perdew-Burke-Ernzerhof density functional confirms the relevance of this double-hybrid model.