Comparison of the structural and electronic properties of two cobalt perovskites, in which Co is formally d6 (LaCoO3), and d7 (KCoF3)
Platonenko, A., El-Kelany, K., Sambrano, J., Doll, K., Dovesi, R. (2025). Comparison of the structural and electronic properties of two cobalt perovskites, in which Co is formally d6 (LaCoO3), and d7 (KCoF3). EKB Journal Management System, 1(1), 34-45. doi: 10.21608/jcmr.2024.329859.1004
Alexander Platonenko; Khaled E. El-Kelany; Julio Sambrano; Klaus Doll; Roberto Dovesi. "Comparison of the structural and electronic properties of two cobalt perovskites, in which Co is formally d6 (LaCoO3), and d7 (KCoF3)". EKB Journal Management System, 1, 1, 2025, 34-45. doi: 10.21608/jcmr.2024.329859.1004
Platonenko, A., El-Kelany, K., Sambrano, J., Doll, K., Dovesi, R. (2025). 'Comparison of the structural and electronic properties of two cobalt perovskites, in which Co is formally d6 (LaCoO3), and d7 (KCoF3)', EKB Journal Management System, 1(1), pp. 34-45. doi: 10.21608/jcmr.2024.329859.1004
Platonenko, A., El-Kelany, K., Sambrano, J., Doll, K., Dovesi, R. Comparison of the structural and electronic properties of two cobalt perovskites, in which Co is formally d6 (LaCoO3), and d7 (KCoF3). EKB Journal Management System, 2025; 1(1): 34-45. doi: 10.21608/jcmr.2024.329859.1004

Comparison of the structural and electronic properties of two cobalt perovskites, in which Co is formally d6 (LaCoO3), and d7 (KCoF3)

Journal of Current Multidisciplinary Research
Volume 1, Issue 1, January 2025, Page 34-45  XML PDF (859.98 K)
Document Type: Original Article
DOI: 10.21608/jcmr.2024.329859.1004
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Authors
Alexander Platonenkoorcid 1; Khaled E. El-Kelany email orcid 2; Julio Sambranoorcid 3; Klaus Dollorcid 4; Roberto Dovesiorcid 5
1Institute of Solid State Physics, University of Latvia, 8 Kengaraga street, LV1063, Riga, Latvia
2Institute of Nanoscience and Nanotechnology, Kafrelsheikh University, 33516 Kafr el-shiekh, Egypt
3Facultate de Ciencias, Sau Paulo State University, Bauru, Brasil
4Institute of Theoretical Chemistry, University of Stuttgart, Molpro Quantum Chemistry Software, Pfaffenwaldring 55, D-70569 Stuttgart, Germany
5ACCADEMIA DELLE SCIENZE DI TORINO,Via Accademia delle Scienze 6, 10123 Torino, (To), Italy
Abstract
Background: The electronic and geometrical properties of LaCoO3, which has a closed shell ground state (Sz=0), are compared with the ones of KCoF3, presenting a high spin (Sz=3/2) ground state. In an ideal fully ionic model, the Co occupancy in the two compounds is d6 (oxide) and d7 (fluoride).
Methods: The analysis of the density of states and of the charge distribution, the latter through a Mulliken analysis, shows that in the oxide the partially covalent character of the Co-O bonds deeply alters the ideal picture, and that not only the t2g, but also the eg subshell is occupied, with an overall d occupancy close to 7 electrons (one electron in the eg subshell), very close to the fluoride occupancy.
Results and conclusion: The deformation with respect to the cubic aristotype (SG 221), down to the tetragonal (SG 123, 127 and 140), orthorhombic (SG 62) and rhombohedral (SG 167) symmetry, with a corresponding increase of the inner degrees of freedom (from 1 to 10) and size of the unit cell (from 5 to 20 atoms), is explored, which confirms that the octahedra remain essentially regular, with an energy gain along the full group-subgroup chain of only 4.6 mEh (0.125 eV) per formula unit. In spite of the similar total occupancy of the d shell, the electronic configuration of Co in KCoF3 is quite different, with a high spin (, with 5α and 2β electrons) ground state.
Keywords
LaCoO$_3$ and KCoF$_3$ perovskites; B3LYP; octahedra rotation; DOS; closed and open shell solutions
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