1,025 research outputs found
Local Self-Energy Approach For Electronic Structure Calculations
Using a novel self-consistent implementation of Hedin's GW perturbation
theory we calculate space and energy dependent self-energy for a number of
materials. We find it to be local in real space and rapidly convergent on
second-- to third-- nearest neighbors. Corrections beyond GW are evaluated and
shown to be completely localized within a single unit cell. This can be viewed
as a fully self consistent implementation of the dynamical mean field theory
for electronic structure calculations of real solids using a perturbative
impurity solver.Comment: 5 pages, 2 figure
Construction of Localized Basis for Dynamical Mean Field Theory
Many-body Hamiltonians obtained from first principles generally include all
possible non-local interactions. But in dynamical mean field theory the
non-local interactions are ignored, and only the effects of the local
interactions are taken into account. The truncation of the non-local
interactions is a basis dependent approximation. We propose a criterion to
construct an appropriate localized basis in which the truncation can be carried
out. This involves finding a basis in which a functional given by the sum of
the squares of the local interactions with appropriate weight factors is
maximized under unitary transformations of basis. We argue that such a
localized basis is suitable for the application of dynamical mean field theory
for calculating material properties from first principles. We propose an
algorithm which can be used for constructing the localized basis. We test our
criterion on a toy model and find it satisfactory
Na Induced Correlations in NaCoO
Increasing experimental evidence is building which indicates that signatures
of strong correlations are present in the Na rich region of NaCoO (ie.
) and absent in the Na poor region (ie. ). This is
unexpected given that NaCoO is a band insulator and CoO has an integer
filled open shell making it a candidate for strong correlations. We explain
these experimental observations by presenting a minimal low-energy Hamiltonian
for the cobaltates and solving it within LDA+DMFT. The Na potential is shown to
be a key element in understanding correlations in this material. Furthermore,
LDA calculations for the realistic Na ordering predict a \emph{binary}
perturbation of the Co sites which correlates with the Na sites (ie. Na
sites above/below Co sites)
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