89 research outputs found
The Generalized SIC-OEP formalism and the Generalized SIC-Slater approximation (stationary and time-dependent cases)
We present a generalized formulation of the Optimized Effective Potential
(OEP) approach to the Self Interaction Correction (SIC) problem in Time
Dependent (TD) Density Functional Theory (DFT). The formulation relies on the
introduction of a double set of single electron orbitals. It allows the
derivation of a generalized Slater approximation to the full OEP formulation,
which extends the domain of validity of the standard Slater approximation. We
discuss both formal aspects and practical applications of the new formalism and
give illustrations in cluster and molecules. The new formalism provides a
valuable ansatz to more elaborate (and computationally very demanding) full TD
OEP and full TD SIC calculations especially in the linear domain
Generalization of internal Density Functional Theory and Kohn-Sham scheme to multicomponent systems, and link with traditional DFT
We generalize the recently developped "internal" Density Functional Theory
(DFT) and Kohn-Sham scheme to multicomponent systems. We obtain a general
formalism, applicable for the description of multicomponent self-bound systems
(as molecules where the nuclei are treated explicitely, atomic nuclei and mix
of 3He and 4He droplets), where the fundamental translational symmetry has been
treated correctly. The main difference with traditional DFT is the explicit
inclusion of center-of-mass correlations in the functional. A large part of the
paper is dedicated to the application to molecules, which permits among other
to clarify the approximations that underly traditional DFT.Comment: 20 pages, 46 reference
Time-dependent Internal DFT formalism and Kohn-Sham scheme
We generalize to the time-dependent case the stationary Internal DFT /
Kohn-Sham formalism presented in Ref. [14]. We prove that, in the
time-dependent case, the internal properties of a self-bound system (as an
atomic nuclei) are all defined by the internal one-body density and the initial
state. We set-up a time-dependent Internal Kohn-Sham scheme as a practical way
to compute the internal density. The main difference with the traditional DFT /
Kohn-Sham formalism is the inclusion of the center-of-mass correlations in the
functional.Comment: 13 pages. To be published in Phys. Rev.
A review of the use of optimal transport distances for high resolution seismic imaging based on the full waveform
We consider the high-resolution seismic imaging method called full-waveform
inversion (FWI). FWI is a data fitting method aimed at inverting for subsurface
mechanical parameters. Despite the large adoption of FWI by the academic and
industrial communities, and many successful results, FWI still suffers from
severe limitations. From a mathematical standpoint, FWI is a large scale
PDE-constrained optimization problem. The misfit function that is used, which
measures the discrepancy between observed seismic data and data calculated
through the solution of a wave propagation problem, is non-convex. After
discretization, the size of the FWI problem requires the use of local
optimization solvers, which are prone to converge towards local minima. Thus
the success of FWI strongly depends on the choice of the initial model to
ensure the convergence towards the global minimum of the misfit function.
This limitation has been the motivation for a large variety of strategies.
Among the different methods that have been investigated, the use of optimal
transport (OT) distances-based misfit functions has been recently promoted. The
leading idea is to benefit from the inherent convexity of OT distances with
respect to dilation and translation to render the FWI problem more convex.
However, the application of OT distances in the framework of FWI is not
straightforward, as seismic data is signed, while OT has been developed for the
comparison of probability measures.
The purpose of this study is to review two methods that were developed to
overcome this difficulty. Both have been successfully applied to field data in
an industrial framework. Both make it possible to better exploit the seismic
data, alleviating the sensitivity to the initial model and to various
conventional workflow steps, and reducing the uncertainty attached to the
subsurface mechanical parameters inversion.Comment: 18 figure
Polarizibilities as a test of localized approximations to the self-interaction correction
We present applications of the recently introduced ``Generalized SIC-Slater''
scheme which provides a simple Self-Interaction Correction approximation in the
framework of the Optimized Effective Potential. We focus on the computation of
static polarizabilities which are known to constitute stringent tests for
Density Functional Theory. We apply the new method to model H chains, but also
to more realistic systems such as C4 (organic) chains, and less symmetrical
systems such as a Na5 (metallic) cluster. Comparison is made with other SIC
schemes, especially with the standard SIC-Slater one.Comment: 17 pages, 4 figures, 49 reference
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