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A Heterogeneous CPU + GPU Algorithm for Variational Two-Electron Reduced-Density Matrix Driven Complete Active Space Self-Consistent Field Theory

preprint
submitted on 26.07.2019 and posted on 26.07.2019 by J. Wayne Mullinax, Elvis Maradzike, Lauren N. Koulias, Mohammad Mostafanejad, Evgeny Epifanovsky, Gergely Gidofalvi, Eugene DePrince

We present a heterogeneous CPU+GPU algorithm for the direct variational optimization of the two-electron reduced-density matrix (2RDM) under two-particle N-representability conditions. This variational 2RDM (v2RDM) approach is the driver for a polynomially-scaling approximation to configuration-interaction-driven complete active space self-consistent field (CASSCF) theory. For v2RDM-based CASSCF com- putations involving an active space consisting of 50 electrons in 50 orbitals [denoted (50e,50o)], we observe a speedup of a factor of 3.7 when the code is executed on a combination of an NVIDIA TITAN V GPU and an Intel Core i7-6850k CPU, relative to the case when the code is executed on the CPU alone. We use this GPU-accelerated v2RDM-CASSCF algorithm to explore the electronic structure of the 3,k-circumacene and 3,k-periacene series (k=2–7) and compare indicators of polyradical character in the lowest-energy singlet states to those observed for oligoacene molecules. The singlet states in larger circumacene and periacene molecules display the same polyradical characteristics observed in oligoacenes, with the onset of this behavior occuring at smallest k for periacenes, followed by the circumacenes and then the oligoacenes. However, the unpaired electron density that accumulates along the zig-zag edge of the circumacenes is slightly less than that which accumulates in the oligoacenes, while periacenes clearly exhibit the greatest build-up of unpaired electron density in this region.

Funding

This material is based upon work supported by the Army Research Office Small Business Technology Transfer (STTR) program under Grant No. W911NF-16- C-0124.

History

Email Address of Submitting Author

adeprince@fsu.edu

Institution

Florida State University

Country

United States of America

ORCID For Submitting Author

0000-0003-1061-2521

Declaration of Conflict of Interest

No conflict of interest.

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