title: Random phase approximation with second-order screened exchange for current-carrying atomic states.
abstract: The direct random phase approximation (RPA) and RPA with second-order screened exchange (SOSEX) have been implemented with complex orbitals as a basis for treating open-shell atoms. Both RPA and RPA+SOSEX are natural implicit current density functionals because the paramagnetic current density implicitly is included through the use of complex orbitals. We confirm that inclusion of the SOSEX correction improves the total energy accuracy substantially compared to RPA, especially for smaller-Z atoms. Computational complexity makes post self-consistent-field (post-SCF) evaluation of RPA-type expressions commonplace, so orbital basis origins and properties become important. Sizable differences are found in correlation energies, total atomic energies, and ionization energies for RPA-type functionals evaluated in the post-SCF fashion with orbital sets obtained from different schemes. Reference orbitals from Kohn-Sham calculations with semi-local functionals are more suitable for RPA+SOSEX to generate accurate total energies, but reference orbitals from exact exchange (non-local) yield essentially energetically degenerate open-shell atom ground states. RPA+SOSEX correlation combined with exact exchange calculated from a hybrid reference orbital set (half the exchange calculated from exact-exchange orbitals, the other half of the exchange from orbitals optimized for the Perdew-Burke-Ernzerhof (PBE) exchange functional) gives the best overall performance. Numerical results show that the RPA-like functional with SOSEX correction can be used as a practical implicit current density functional when current effects should be included.
authors.affiliation: Department of Physics, Hangzhou Normal University, 16 Xuelin Street, Hangzhou, Zhejiang 310036, China.
authors.forename: Wuming
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Institute of Service Engineering, Hangzhou Normal University, 2318 Yuhangtang Road, Cangqian, Hangzhou, Zhejiang 311121, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Quantum Theory Project, Department of Physics and Department of Chemistry, University of Florida, P.O. Box 118435, Gainesville, Florida 32611-8435, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Trickey