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Developing orbital‐free quantum crystallography: the local potentials and associated partial charge densities
Author(s) -
Tsirelson Vladimir,
Stash Adam
Publication year - 2021
Publication title -
acta crystallographica section b
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.604
H-Index - 33
ISSN - 2052-5206
DOI - 10.1107/s2052520621005540
Subject(s) - density functional theory , pauli exclusion principle , orbital free density functional theory , crystal (programming language) , chemistry , electron , electron density , electrostatics , physics , quantum mechanics , molecular physics , atomic physics , computational chemistry , hybrid functional , computer science , programming language
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.