Abstract
Can an electronic device be constructed using only a single molecule? Since this question was first asked by Aviram and Ratner in the 1970s [Chem. Phys. Lett. 29, 277 (1974)], the field of molecular electronics has exploded with significant experimental advancements in the understanding of the charge transport properties of single molecule devices. Efforts to explain the results of these experiments and identify promising new candidate molecules for molecular devices have led to the development of numerous new theoretical methods including the current standard theoretical approach for studying single molecule charge transport, i.e., the non-equilibrium Green's function formalism (NEGF). By pairing this formalism with density functional theory (DFT), a wide variety of transport problems in molecular junctions have been successfully treated. For some systems though, the conductance and current-voltage curves predicted by common DFT functionals can be several orders of magnitude above experimental results. In addition, since density functional theory relies on approximations to the exact exchange-correlation functional, the predicted transport properties can show significant variation depending on the functional chosen. As a first step to addressing this issue, the authors have replaced density functional theory in the NEGF formalism with a 2-electron reduced density matrix (2-RDM) method, creating a new approach known as the NEGF-RDM method. 2-RDM methods provide a more accurate description of electron correlation compared to density functional theory, and they have lower computational scaling compared to wavefunction based methods of similar accuracy. Additionally, 2-RDM methods are capable of capturing static electron correlation which is untreatable by existing NEGF-DFT methods. When studying dithiol alkane chains and dithiol benzene in model junctions, the authors found that the NEGF-RDM predicts conductances and currents that are 1-2 orders of magnitude below those of B3LYP and M06 DFT functionals. This suggests that the NEGF-RDM method could be a viable alternative to NEGF-DFT for molecular junction calculations.
Original language | English (US) |
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Article number | 184110 |
Journal | Journal of Chemical Physics |
Volume | 147 |
Issue number | 18 |
DOIs | |
State | Published - Nov 14 2017 |
Funding
The authors would like to thank the National Science Foundation (Award No. CHE-146501) for supporting this work. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation (Award No. ACI-1548562). D.A.M. gratefully acknowledges the U.S. National Science Foundation Grant No. CHE-1565638 and the U.S. Army Research Office (ARO) Grant No. W911NF-16-1-0152 for support.
ASJC Scopus subject areas
- General Physics and Astronomy
- Physical and Theoretical Chemistry