arXiv subjects

Werner Hofer

Publications and source records attributed to Werner Hofer.

4 recordsLinked to original sources

arXiv2020

Exact kinetic energy functional for general many-electron systems

The exact form of the kinetic energy functional has remained elusive in orbital-free models of density functional theory (DFT). This has been the main stumbling block for the development of a general-purpose framework on this basis. Here, we show that on the basis of a two-density model, which represents many-electron systems by mass density and spin density components, we can derive the exact form of such a functional. The exact functional is shown to contain previously suggested functionals to some extent, with the notable exception of the Thomas-Fermi kinetic energy functional.

cond-mat.mes-hall↗

arXiv2018

A two-density approach to the general many-body problem and a proof of principle for small atoms and molecules

An extended electron model fully recovers many of the experimental results of quantum mechanics while it avoids many of the pitfalls and remains generally free of paradoxes. The formulation of the many-body electronic problem here resembles the Kohn-Sham formulation of standard density functional theory. However, rather than referring electronic properties to a large set of single electron orbitals, the extended electron model uses only mass density and field components, leading to a substantial increase in computational efficiency. To date, the Hohenberg-Kohn theorems have not been proved for a model of this type, nor has a universal energy functional been presented. In this paper, we address these problems and show that the Hohenberg-Kohn theorems do also hold for a density model of this type. We then present a proof-of-concept practical implementation of this method and show that it reproduces the accuracy of more widely used methods on a test-set of small atomic systems, thus paving the way for the development of fast, efficient and accurate codes on this basis.

physics.comp-ph↗

arXiv2017

Spin in the extended electron model

It has been found that a model of extended electrons is more suited to describe theoretical simulations and experimental results obtained via scanning tunnelling microscopes, but while the dynamic properties are easily incorporated, magnetic properties, and in particular electron spin properties pose a problem due to their conceived isotropy in the absence of measurement. The spin of an electron reacts with a magnetic field and thus has the properties of a vector. However, electron spin is also isotropic, suggesting that it does not have the properties of a vector. This central conflict in the description of an electron's spin, we believe, is the root of many of the paradoxical properties measured and postulated for quantum spin particles. Exploiting a model in which the electron spin is described consistently in real three-dimensional space - an extended electron model - we demonstrate that spin may be described by a vector and still maintain its isotropy. In this framework, we re-evaluate the Stern-Gerlach experiments, the Einstein-Podolsky-Rosen experiments, and the effect of consecutive measurements and find in all cases a fairly intuitive explanation.

physics.gen-ph↗

arXiv2013

The Origin of Half-Metallicity in Conjugated Electron System -- a Study on Transition Metal Doped Graphyne

We studied the mechanism of half-metallicity (HM) formation in transition metal doped (TM) conjugated carbon based structures by first-principles electronic structure simulations. It is found that the HM is a rather complex phenomenon, determined by the ligand field splitting of d-orbitals of the transition metal (TM) atoms, the exchange splitting and the number of valence electrons. Since most of the conjugated carbon based structures possess ligands with intermediate strength, the ordering of the d-orbital splitting is similar in all structures, and the HM properties evolve according to the number of valence electrons. Based on this insight we predict that Cr-, Fe-, Co-doped graphyne will show HM, while Mn- and Ni-doped graphyne will not. By tuning the number of valence electron, we are thus able to control the emergence of HM and control the energy gaps evolving in majority or minority spin channels.

cond-mat.mes-hall↗