How Well Can Parametrized and Parameter-Free Double-Hybrid Approximations Predict Response Properties of Hydrogen-Bonded Systems? Dipole Polarizabilities of Water Nanoclusters as a Working Model

The development of double-hybrid (DH) density functional approximations has been a crucial ingredient in the success of density functional theory (DFT). To further extend the range of applicability of these approximations, their suitability for investigating the response of hydrogen-bonded systems to external static electric fields is explored here. As a case study, we focus on the performance of parametrized and parameter-free DH density functionals for calculations of isotropic and anisotropic dipole polarizabilities of water nanoclusters. The functionals considered in our study are B2GP-PLYP, B2-PLYP, mPW2-PLYP, and SD-PBEP86 as parametrized functionals, and PBE0-DH and PBE0-2 as parameter-free models. The second-order Moller-Plesset perturbation theory (MP2) as a wave function theory (WFT) based method is also included for the sake of comparison. As a reference for methods benchmarking, the results of coupled-cluster method with single and double excitations (CCSD) are used. Scrutinizing the role of exchange, correlation, and their contributions in the functionals reveals that PBE0-DH is the best method that predicts the most accurate isotropic polarizabilities by a large margin with respect to other tested functionals. Moreover, we found that the PBE0-DH has a smaller mean absolute deviation than MP2. On the other hand, our results show that PBE0-2 outperforms other methods for anisotropic polarizabilities of clusters studied. On the whole, among all the tested DH density functionals for dipole polarizabilities of water clusters, the parameter-free PBE-based models are found to offer the best overall performance.