Electronic states and localization in nanoscopic chains and rings from   first principles: EDABI method
  We summarize briefly the main results obtained within the proposed EDABI method combining Exact Diagonalization of (parametrized) many-particle Hamiltonian with Ab Initio self-adjustment of the single-particle wave function in the correlated state of interacting electrons. The properties of nanoscopic chains and rings are discussed as a function of their interatomic distance R and compared with those obtained by Bethe ansatz for infinite Hubbard chain. The concepts of renormalized orbitals, distribution function in momentum space, and of Hubbard splitting as applied to nanoscopic systems are emphasized. 
E. M. Gorlich, J. Kurzyk, A. Rycerz, R. Zahorbenski, R. Podsiadly, W.   Wojcik, J. Spalek