Ab initio cluster studies of La sub 2 CuO sub 4
In this paper we examine the properties of small cluster models of La{sub 2}CuO{sub 4}. In Section 2, the Madelung/Pauli background potential used to imbed the primary cluster and the basis sets used to expand the cluster wavefunction are discussed. Section 3 presents the results of calculations on CuO{sub 6} in which the optical absorption and the photoemission spectrum are examined. The calculation on CuO{sub 6} and our earlier work on larger clusters suggest that a single-band Pariser-Parr-Pople (PPP) model be developed. Therefore, in Section 4 the PPP model and extensions which relax the zero-differential-overlap (ZDO) approximation upon which it is based are reviewed. Calculations on the states of Cu{sub 2}O{sub 7} necessary to parameterize the PPP model are presented in Section 5 and compared with analogous calculations for Cu{sub 2}O{sub 11}. Section 6 discusses the problems associated with the direct ab initio determination of the anti-ferromagnetic exchange interaction, examines the magnitudes of the occupation-dependent hopping and direct exchange interactions which arise when the ZDO approximation is relaxed, and provides estimates of the uncertainties in the parameters due to electron correlation and polarization effects not recoverable with the present basis sets and finite clusters. A comparison of the parameters with those extracted from constrained LDF theory concludes Section 6. Finally, Section 7 summarizes the conclusions of this research.
- Research Organization:
- Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (USA)
- DOE Contract Number:
- W-7405-ENG-36
- OSTI ID:
- 5570470
- Report Number(s):
- LA-UR-91-1517; CONF-9104262-1; ON: DE91013520
- Resource Relation:
- Conference: North Atlantic Treaty Organization (NATO) advanced research workshop on cluster models for surface and bulk phenomena, Sicily (Italy), 19-26 Apr 1991
- Country of Publication:
- United States
- Language:
- English
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