One of the central challenges of quantum chemistry is accurate prediction of electronic structure of nanoscale systems and their response to external perturbations with the final goal to develop a molecular level understanding and reach quantitative level of theoretical prediction.<br/>Advancement of fabrication techniques at the nanoscale has led to a surge of experimental activity in constructing nanodevices, thus extending the challenge to theory into the realm of open systems far from equilibrium. Theoretical simulations of open non-equilibrium systems at nanoscale mostly employ single-particle basis (e.g. orbitals as in NEGF-DFT). These approaches allow treating systems of realistic sizes, but become inconvenient in treating strong system interactions. An alternative approach (e.g. PP- or Hubbard NEGF) utilizes many-body states of the isolated system as a basis, which allows accounting for the system interactions, however applicability of such formulations is limited to relatively small systems. I will discuss our efforts in developing a methodologies based on the many-body states formulation, <i>the nonequilibrium atomic limit</i>, thier applications to simulations of transport and optical response in junctions, and efforts in forumlations of the non-equilibrium divide-and-conquer method, which will capitalize on strong sides of both the NEGF-DFT ability to treat big systems and the PP- and Hubbard NEGF ability to account for strong local interactions exactly.

Non-equilibrium atomic limit and divide-and-conquer method for nanoscale simulations

251st National Meeting (2016)

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