scholarly journals Reduced density matrix sampling: Self-consistent embedding and multiscale electronic structure on current generation quantum computers

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Jules Tilly ◽  
P. V. Sriluckshmy ◽  
Akashkumar Patel ◽  
Enrico Fontana ◽  
Ivan Rungger ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Density Matrix ◽  
Reduced Density Matrix ◽  
Quantum Computers ◽  
Current Generation ◽  
Matrix Sampling ◽  
Self Consistent ◽  
Reduced Density

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

2019 ◽  
Author(s):  
J. Wayne Mullinax ◽  
Elvis Maradzike ◽  
Lauren N. Koulias ◽  
Mohammad Mostafanejad ◽  
Evgeny Epifanovsky ◽  
...  
Keyword(s):  
Density Matrix ◽  
Reduced Density Matrix ◽  
Complete Active Space ◽  
Active Space ◽  
Consistent Field ◽  
Singlet States ◽  
Unpaired Electron Density ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Reduced Density

<div><div><div><p>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.</p></div></div></div>

Energies and structures in biradical chemistry from the parametric two-electron reduced-density matrix method: applications to the benzene and cyclobutadiene biradicals

2015 ◽  
Vol 17 (19) ◽  
pp. 12521-12529 ◽  
Author(s):  
Alison L. McManus ◽  
Erik P. Hoy ◽  
David A. Mazziotti
Keyword(s):  
Electronic Structure ◽  
Density Matrix ◽  
Electron Correlation ◽  
Matrix Method ◽  
Electronic Structure Theory ◽  
Reduced Density Matrix ◽  
Structure Theory ◽  
Reference Methods ◽  
Reduced Density

The treatment of biradical chemistry presents a challenge for electronic structure theory, especially single-reference methods, as it requires the description of varying degrees and kinds of electron correlation.

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