6,821 research outputs found
Correlation energy, pair-distribution functions and static structure factors of jellium
We discuss and clarify a simple and accurate interpolation scheme for the
spin-resolved electron static structure factor (and corresponding pair
correlation function) of the 3D unpolarized homogeneous electron gas which,
along with some analytic properties of the spin-resolved pair-correlation
functions, we have just published. We compare our results with the very recent
spin-resolved scheme by Schmidt et al., and focus our attention on the
spin-resolved correlation energies and the high-density limit of the
correlation functions.Comment: 8 pages, 3 figures. Proceedings of the conference on Statistical
Mechanics and Strongly Correlated Systems (Bachelet, Parisi & Vulpiani Eds.)
to appear as a special issue of Physica A (Elsevier, Amsterdam 2000
Spin-state transition and spin-polaron physics in cobalt oxide perovskites: ab initio approach based on quantum chemical methods
A fully ab initio scheme based on quantum chemical wavefunction methods is
used to investigate the correlated multiorbital electronic structure of a
3d-metal compound, LaCoO3. The strong short-range electron correlations,
involving both Co and O orbitals, are treated by multireference techniques. The
use of effective parameters like the Hubbard U and interorbital U', J terms and
the problems associated with their explicit calculation are avoided with this
approach. We provide new insight into the spin-state transition at about 90 K
and the nature of charge carriers in the doped material. Our results indicate
the formation of a t4e2 high-spin state in LaCoO3 for T>90 K. Additionally, we
explain the paramagnetic phase in the low-temperature lightly doped compound
through the formation of Zhang-Rice-like O hole states and ferromagnetic
clusters
Ground-state properties of rutile: electron-correlation effects
Electron-correlation effects on cohesive energy, lattice constant and bulk
compressibility of rutile are calculated using an ab-initio scheme. A
competition between the two groups of partially covalent Ti-O bonds is the
reason that the correlation energy does not change linearly with deviations
from the equilibrium geometry, but is dominated by quadratic terms instead. As
a consequence, the Hartree-Fock lattice constants are close to the experimental
ones, while the compressibility is strongly renormalized by electronic
correlations.Comment: 1 figure to appear in Phys. Rev.
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