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Ab initio electronic structure theory for a cluster model of La 2– x Sr x CuO 4
Author(s) -
Martin Richard L.,
Saxe Paul W.
Publication year - 1988
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560340828
Subject(s) - ab initio , condensed matter physics , ground state , electronic structure , hamiltonian (control theory) , coupled cluster , chemistry , degenerate energy levels , spins , ab initio quantum chemistry methods , cluster (spacecraft) , valence bond theory , doping , physics , atomic physics , molecular orbital , quantum mechanics , molecule , mathematical optimization , mathematics , computer science , programming language
We report the results of ab initio calculations on a model Cu 4 O 12 cluster. The spectrum of the undoped cluster is most appropriately described in a localized valence bond framework. The ground state and low lying excitations can be fit quite well to a Heisenberg Hamiltonian with an anti‐ferromagnetic coupling constant between nearest‐neighbor Cu3 d spins. For a doping level x = 0.25, the electronic states are most easily interpreted in a molecular orbital (Fermi liquid) framework. In addition, doping introduces low‐lying Cu ⟷ O charge transfer excitations. Our best calculations to date associate the ground state with a hole in the Cu3 d anti‐bonding band (Cu 3+ O 2− ), but the state in which the hole is associated with the O2 p band (Cu 2+ O 1− ) is nearly degenerate.