M. Divis et V. Nekvasil, Semi-empirical and ab-initio calculations of the crystal field interactionin rare earth cuprates, J ALLOY COM, 323, 2001, pp. 567-571
Semi-empirical and ab-initio methods useful for theoretical investigations
of the crystal field (CF) interaction in rare earth (RE) cuprates are descr
ibed. Concrete calculations are performed for Sm1+xBa2-xCu3O6+y a system pr
oviding detailed data on intermultiplet infrared-active CF transitions for
Sm3+ ions on the regular D-4h symmetry sites as well as on the substituted
C-4v. symmetry Ba sites. Within this study, the main attention is paid to t
he second order CF parameters calculated using a parameter free first princ
iples method based on the density functional theory (DFT). A general potent
ial linearized augmented plane wave (LAPW) computational method is used to
obtain the ground state charge density. The calculated value of B-20 = 320
cm(-1) in D-4h symmetry sites of Sm is in a good agreement with the phenome
nological value of 282 cm(-1) obtained from a fit to infrared transmission
spectroscopy data. For Sm in the C-4v symmetry sites, the DFT value of B-20
= -227 cm(-1) together with the standard superposition model values, B-40
=24, B-44 = -331, B-60 = - 427 and B-64 =624 cm(-1), allow us to interpret
the main features of the available infrared absorption data. It is shown th
at the sign of the B-20 in SmBa2Cu3O6+y, positive in the regular sites and
negative in the Ba sites, is governed by the shape of the crystal potential
within the LAPW atomic sphere of Sm atom. (C) 2001 Elsevier Science B.V. A
ll rights reserved.