Gw. Burdick et Fs. Richardson, APPLICATION OF THE CORRELATION-CRYSTAL-FIELD DELTA-FUNCTION MODEL IN ANALYSES OF PR3-LEVEL STRUCTURES IN CRYSTALLINE HOSTS((4F(2)) ENERGY), Chemical physics, 228(1-3), 1998, pp. 81-101
The 4f(2) electronic energy-level structures observed for Pr3+ in seve
n different crystalline host materials are analyzed and compared. The
analyses are based on a model Hamiltonian that includes consideration
of both one-electron crystal-field (CF) and two-electron correlation-c
rystal-field (CCF) interactions. Special attention is given to the imp
ortance of CCF interactions in determining the crystal-field energy-le
vel structures observed within particular anomalous multiplet manifold
s of Pr3+ such as the D-1(2) and (1)G(4) multiplets, which typically e
xhibit crystal-field energy-level structures that cannot be explained
in terms of 'standard' one-electron CF interaction models. It is shown
in the present study that the apparently anomalous behavior of these
multiplets can be explained in terms of two-electron CCF effects. It i
s further shown that the relevant CCF effects can be satisfactorily mo
deled by use of a highly restricted 'delta-function' form of the gener
al two-electron CCF model Hamiltonian, where the dominant two-electron
correlation effects are assumed to arise from spin-paired electrons o
ccupying the same angular orbital. Incorporation of this restricted CC
F model Hamiltonian into the modeling calculations requires the introd
uction of only one or two additional parameters beyond those required
for the standard one-electron CF modeling calculations, and satisfacto
rily resolves the major discrepancies between observed and calculated
crystal-field splittings for the anomalous D-1(2) and (1)G(4) multiple
t manifolds in the energy-level structures of LaCl3:Pr3+, GdCl3:Pr3+ C
s2NaPrCl6, Cs2NaYCl6:Pr3+, LiYF4:Pr3+, LiBiF4:Pr3+, and CsCdBr3:Pr3+.
(C) 1998 Elsevier Science B.V.