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Title: Communication: Fragment-based Hamiltonian model of electronic charge-excitation gaps and gap closure

Capturing key electronic properties such as charge excitation gaps within models at or above the atomic scale presents an ongoing challenge to understanding molecular, nanoscale, and condensed phase systems. One strategy is to describe the system in terms of properties of interacting material fragments, but it is unclear how to accomplish this for charge-excitation and charge-transfer phenomena. Hamiltonian models such as the Hubbard model provide formal frameworks for analyzing gap properties but are couched purely in terms of states of electrons, rather than the states of the fragments at the scale of interest. The recently introduced Fragment Hamiltonian (FH) model uses fragments in different charge states as its building blocks, enabling a uniform, quantum-mechanical treatment that captures the charge-excitation gap. These gaps are preserved in terms of inter-fragment charge-transferhopping integrals T and on-fragment parameters U (FH). The FH model generalizes the standard Hubbard model (a single intra-band hopping integral t and on-site repulsion U) from quantum states for electrons to quantum states for fragments. In this paper, we demonstrate that even for simple two-fragment and multi-fragment systems, gap closure is enabled once T exceeds the threshold set by U (FH), thus providing new insight into the nature of metal-insulator transitions.more » Finally, this result is in contrast to the standard Hubbard model for 1d rings, for which Lieb and Wu proved that gap closure was impossible, regardless of the choices for t and U.« less
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  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Materials Science and Technology Division
  2. Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Physics and Astronomy
Publication Date:
Report Number(s):
Journal ID: ISSN 0021-9606
Grant/Contract Number:
AC52-06NA25396; 2008LANL1026; HDTRA1-09-1-008
Published Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 143; Journal Issue: 18; Journal ID: ISSN 0021-9606
American Institute of Physics (AIP)
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); Defense Threat Reduction Agency (DTRA)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1329873; OSTI ID: 1421243