报告题目：Recent advances on the XYG3-type of doubly hybrid densityfunctionals
Doubly hybrid (DH) functionals present a new class of density functionals, which enfold the non-local orbital-dependent components not only in the exchange part, but also in the correlation part. Different types of DH functionals have been proposed according to different philosophies [1-3], where the XYG3-type of functionals (xDH) [3-11] is unique in its framework that a conventional (general) Kohn-Sham (KS) functional, such as B3LYP [3-6] or PBE0  or PBE , is utilized for the self-consistent-field (SCF) calculations to generate orbitals and density, with which a DH functional is used for the final energy evaluations.
This talk focuses on our recent efforts in the development of the xDH functionals. (1) A long-range-corrected XYG3 (i.e., lrc-XYG3) is developed, which includes a range-dependent term from the second order perturbation theory for better description of dispersive interaction . (2) Analytic gradients are developed, where the non-variational contributions from the SCF functional to the final energy functional are solved through a coupled-perturbed KS equation [9, 10]. (3) Fractional charge behaviours of DH functionals are explored [11,12], which lead to good predictions of ionization potentials, electron affinities and fundamental gaps from the perspective of fractional charges. (4) A non-fitted DH functional, namely PBE-ACDH, is constructed based on the adiabatic connection (AC) formalism, coordinate scaling relations, and the second order G?rling-Levy perturbation theory , where contributions from density scaling and singles are explicitly considered.
Limitations of the present approaches and the direction for future improvements will be discussed.
This research was sponsored by the Ministry of Science and Technology of China (2013CB834606, 2011CB808505), and National Natural Science Foundation of China (21133004, 91427301).
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