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How to tell an atom from an electron gas: a semi-local index of density inhomogeneity
Department of Physics and Quantum Theory Group, Tulane University, New Orleans,.
Department of Physics and Quantum Theory Group, Tulane University, New Orleans,.
KTH, Superseded Departments, Physics.
2003 (English)In: Acta physica et chimica debrecina, Vol. 36, no 25Article in journal (Refereed) Published
Abstract [en]

From a global perspective, the density of an atom is strongly inhomogeneous and not at all like the density of a uniform or nearly-uniform electron gas. But, from the semi-local or myopic perspective of standard density functional approximations to the exchange-correlation energy, it is not so easy to tell an atom from an electron gas. We address the following problem:  Given the ground-state electron density n and orbital kinetic energy density in the neighborhood of a point r, can we construct an inhomogeneity index which approaches zero for weakly-inhomogeneous densities and unity for strongly-inhomogeneous ones? The solution requires not only the usual local ingredients of a meta-generalized gradient approximation, but also r and r2. The inhomogeneity index is displayed for atoms, and for model densities of metal surfaces and bulk metals. Scaling behavior and a possible application to functional interpolation are discussed.



Place, publisher, year, edition, pages
2003. Vol. 36, no 25
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-6785OAI: oai:DiVA.org:kth-6785DiVA: diva2:11594
Note
QC 20100830Available from: 2005-09-23 Created: 2005-09-23 Last updated: 2010-08-31Bibliographically approved
In thesis
1. The many-electron energy in density functional theory: from exchange-correlation functional design to applied electronic structure calculations
Open this publication in new window or tab >>The many-electron energy in density functional theory: from exchange-correlation functional design to applied electronic structure calculations
2005 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [sv]

Att förutsäga egenskaper hos material och kemiska system är en viktig komponent för teoretisk och teknisk utveckling i fysik, kemi och biologi. Ett systems egenskaper styrs till stor del av dess elektrontillstånd. Datorprogram som baseras på täthetsfunktionalsteori kan beskriva elektronkonfigurationer mycket noggrant. Täthetsfunktionalsteorin hanterar all kvantmekanisk energi exakt, förutom ett mindre bidrag, utbytes-korrelationsenergin. Avhandlingen diskuterar existerande approximationer av utbytes-korrelationsenergin och presenterar en ny metod för konstruktion av funktionaler som hanterar detta bidrag---delsystems-funktionalmetoden. Flera teoretiska resultat relaterade till funktionalutveckling ges. En utbytes-korrelations-funktional har konstruerats helt utan empiriska antaganden (dvs, från första-princip). Funktionalen har använts för att beräkna gitterkonstant, bulkmodul och vakansenergi för aluminium, platina och kisel. Arbetet förväntas vara generellt tillämpbart inom området för täthetsfunktionalsteoriberäkningar

Abstract [en]

The prediction of properties of materials and chemical systems is a key component in theoretical and technical advances throughout physics, chemistry, and biology. The properties of a matter system are closely related to the configuration of its electrons. Computer programs based on density functional theory (DFT) can calculate the configuration of the electrons very accurately. In DFT all the electronic energy present in quantum mechanics is handled exactly, except for one minor part, the exchange-correlation (XC) energy. The thesis discusses existing approximations of the XC energy and presents a new method for designing XC functionals---the subsystem functional scheme. Numerous theoretical results related to functional development in general are presented. An XC functional is created entirely without the use of empirical data (i.e., from so called first-principles). The functional has been applied to calculations of lattice constants, bulk moduli, and vacancy formation energies of aluminum, platinum, and silicon. The work is expected to be generally applicable within the field of computational density functional theory.

Place, publisher, year, edition, pages
Stockholm: KTH, 2005. ix, 85 p.
Series
Trita-FYS, ISSN 0280-316X ; 2005:48
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-428 (URN)91-7178-150-1 (ISBN)
Public defence
2005-09-30, Sal FR4, AlbaNova, Roslagstullsbacken 21, Stockholm, 14:00
Opponent
Supervisors
Note
QC 20100830Available from: 2005-09-23 Created: 2005-09-23 Last updated: 2010-08-31Bibliographically approved

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