https://doi.org/10.1140/epjb/e2008-00263-1
Ab initio cluster calculations of Co3+ spin states in RBaCo2O5.5 (R = Ho, Gd)
1
Max-Planck-Institut für Physik Komplexer Systeme, Nöthnitzer Straße 38, 01187 Dresden, Germany
2
Joint Institute for Nuclear Research, 141980 Dubna, Russia
3
Physikalische und Theoretische Chemie, Freie Universität Berlin, Takustraße 3, 14195 Berlin, Germany
4
Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187 Dresden, Germany
Corresponding author: a siuraksh@jinr.ru
Received:
12
February
2008
Published online:
10
July
2008
Two types of oxygen-deficient perovskites RBaCo2O5.5(R = Ho, Gd) related to the “122" type structure (ap × 2ap × 2ap) have been studied on the basis of ab initio cluster calculations. We consider the peculiar behavior of the trivalent ions Co3+(3d6) in either octahedral or pyramidal oxygen coordinations, which is related to a structural first-order phase transition in both compounds. Relative energy positions of low spin (LS, S = 0), intermediate spin (IS, S = 1) and high spin (HS, S = 2) electron configurations are calculated for the low- and high-temperature lattice structures of RBaCo2O5.5. A combined analysis of the calculated results and experimental structural data leads to a simple model that captures the most prominent features of the phase transition common to both compounds.
PACS: 71.70.-d – Level splitting and interactions / 71.15.-m – Methods of electronic structure calculations
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2008