Detailed analysis of deformation potentials with application in orbital-free density functional theory

A detailed analysis of the recently published deformation potentials for application in orbital-free density functional theory is given. Since orbital-free density functional theory is a purely density-based description of quantum mechanics, it may in the future provide itself useful in quantum crystallography as it establishes a direct link between experiment and theory via a single meaningful quantity: the electron density. In order to establish this goal, sufficiently accurate approximations for the kinetic energy have to be found. The present work is a further step in this direction. The so-called deformation potentials allow the interaction between the atoms to be taken into account through the help of their electron density only. It is shown that the present ansatz provides a systematic pathway beyond the recently introduced atomic fragment approach.

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Developing orbital-free quantum crystallography: the local potentials and associated partial charge densities

Acta Crystallographica Section B Structural Science Crystal Engineering and Materials ◽

10.1107/s2052520621005540 ◽

2021 ◽

Vol 77 (4) ◽

Author(s):

Vladimir Tsirelson ◽

Adam Stash

Keyword(s):

Density Functional Theory ◽

Electron Density ◽

Density Functional ◽

Electronic Energy ◽

Physical Content ◽

Functional Theory ◽

Orbital Free ◽

The One ◽

Physical And Chemical ◽

Quantum Crystallography

This work extends the orbital-free density functional theory to the field of quantum crystallography. The total electronic energy is decomposed into electrostatic, exchange, Weizsacker and Pauli components on the basis of physically grounded arguments. Then, the one-electron Euler equation is re-written through corresponding potentials, which have clear physical and chemical meaning. Partial electron densities related with these potentials by the Poisson equation are also defined. All these functions were analyzed from viewpoint of their physical content and limits of applicability. Then, they were expressed in terms of experimental electron density and its derivatives using the orbital-free density functional theory approximations, and applied to the study of chemical bonding in a heteromolecular crystal of ammonium hydrooxalate oxalic acid dihydrate. It is demonstrated that this approach allows the electron density to be decomposed into physically meaningful components associated with electrostatics, exchange, and spin-independent wave properties of electrons or with their combinations in a crystal. Therefore, the bonding information about a crystal that was previously unavailable for X-ray diffraction analysis can be now obtained.

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Development of novel kinetic energy functional for orbital-free density functional theory applications

International Journal of Modern Physics C ◽

10.1142/s0129183122500449 ◽

2021 ◽

Author(s):

Vittoria Urso

Keyword(s):

Density Functional Theory ◽

Energy Density ◽

Kinetic Energy ◽

Density Functional ◽

Energy Functional ◽

Kinetic Energy Density ◽

Functional Theory ◽

Energy Functionals ◽

Kinetic Energy Functional ◽

Orbital Free

The development of novel Kinetic Energy (KE) functionals is an important topic in density functional theory (DFT). In particular, this happens by means of an analysis with newly developed benchmark sets. Here, I present a study of Laplacian-level kinetic energy functionals applied to metallic nanosystems. The nanoparticles are modeled using jellium sph eres of different sizes, background densities, and number of electrons. The ability of different functionals to reproduce the correct kinetic energy density and potential of various nanoparticles is investigated and analyzed in terms of semilocal descriptors. Most semilocal KE functionals are based on modifications of the second-order gradient expansion GE2 or GE4. I find that the Laplacian contribute is fundamental for the description of the energy and the potential of nanoparticles.

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