Effect of covalency and interactions on the trigonal splitting in Na x CoO2

• Autores: Aligia, Armando Angel
• Año de publicación: 2013
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Covalency; Interactions; Splitting; Naxcoo2
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

We calculate the effective trigonal crystal field Delta that splits the t2g levels of effective models for Nax CoO2 as the local symmetry around a Co ion is reduced from Oh to D3d . To this end, we solve numerically a CoO6 cluster containing a Co ion with all 3d states and their interactions included, and its six nearest-neighbor O atoms, with the geometry of the system, in which the CoO6 octahedron is compressed along a C3 axis. We obtain Delta≈ 130 meV, with the sign that agrees with previous quantum chemistry calculations but disagrees with first-principles results in the local density approximation (LDA). We find that Delta is very sensitive to a Coulomb parameter that controls the Hund coupling and charge distribution among the d orbitals. The origin of the discrepancy with LDA results is discussed.
Fil: Aligia, Armando Angel. Comisión Nacional de Energía Atómica. Gerencia del Area de Investigación y Aplicaciones No Nucleares. Gerencia de Física (Centro Atómico Bariloche); Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte; Argentina