Electronic structure of clusters: Applications to high- Tc superconductors

Miscellaneous · Fri Jan 01 00:00:00 EST 1988

OSTI ID:6071051

Chen, H

A method is presented for studying the electronic structure of clusters by ab initio, self-consistent, local-spin density functional calculations. The linear combination of Gaussian orbitals (LCGO) method was adopted in developing a general cluster program. A variational charge-fitting procedure is used in the evaluation of the matrix elements of the electrostatic potential, and a separate least-squares fitting procedure is used in regard to the exchange-correlation potential. Self-consistent solutions were obtained using this program for the Ba{sub 4}Cu{sub 2}O{sub 7} clusters a portion of the Cu-O chain in the high-{Tc} superconductor YBa{sub 2}Cu{sub 3}O{sub 7}. Four different charge states of Ba{sub 4}Cu{sub 2}O{sub 7} are considered. The spin-polarized calculation predicts zero local moment on Cu sites. The cluster ground state shows strong covalent bonding between the copper and oxygen atoms. Transition-state calculations are made to determine electronic relaxation occurring in photo-emission and to evaluate the Hubbard interaction parameters U{sub dd} and U{sub pp}. We have derived a complete formula to calculate the photo-emission spectrum using the LCGO wave functions. Ultraviolet photoelectron spectra of the YBa{sub 2}Cu{sub 3}O{sub 7} crystal have been calculated. Our results are compared with experiment. Effects of fluorine and nitrogen substitutions to high-{Tc} superconductors are investigated by studying the electronic structure of Ba{sub 4}Cu{sub 2}O{sub 6}N and Ba{sub 4}Cu{sub 2}O{sub 6}F clusters. Results for other interesting systems such as the Fe{sub 2} molecule, the planar CuO{sub 6} and Cu{sub 4}O{sub 4} clusters are also discussed in this work.

• Research Organization: Louisiana State Univ., New Orleans, LA (USA)
• OSTI ID: 6071051
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM COMPOUNDS
CUPRATES
SUPERCONDUCTORS
ELECTRONIC STRUCTURE
ANALYTICAL SOLUTION
SOLID CLUSTERS
YTTRIUM COMPOUNDS
CHARGE STATES
POTENTIALS
TRANSITION TEMPERATURE
ALKALINE EARTH METAL COMPOUNDS
COPPER COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
360204* - Ceramics
Cermets
& Refractories- Physical Properties
656100 - Condensed Matter Physics- Superconductivity