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Subsystem functionals: investigating the exchange energy per particle
KTH, Superseded Departments, Physics.
Interface Sci. Department MS 1415, Sandia National Laboratories, Albuquerque.
2002 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 16, 1651171-16511717 p.Article in journal (Refereed) Published
Abstract [en]

A viable way of extending the successful use of density-functional theory into studies of even more complex systems than are addressed today has been suggested by Kohn and Mattsson [W. Kohn and A. E. Mattsson, Phys. Rev. Lett. 81, 3487 (1998); A. E. Mattsson and W. Kohn, J. Chem. Phys. 115, 3441 (2001)], and is further developed in this work. The scheme consists of dividing a system into subsystems and applying different approximations for the unknown (but general) exchange-correlation energy functional to the different subsystems. We discuss a basic requirement on approximative functionals used in this scheme; they must all adhere to a single explicit choice of the exchange-correlation energy per particle. From a numerical study of a model system with a cosine effective potential, the Mathieu gas, and one of its limiting cases, the harmonic oscillator model, we show that the conventional definition of the exchange energy per particle cannot be described by an analytical series expansion in the limit of slowly varying densities. This indicates that the conventional definition is not suitable in the context of subsystem functionals. We suggest alternative definitions and approaches to subsystem functionals for slowly varying densities and discuss the implications of our findings on the future of functional development.

Place, publisher, year, edition, pages
2002. Vol. 66, no 16, 1651171-16511717 p.
Keyword [en]
Generalized Gradient Approximation, Electron-Gas, Potential Approximation, Metallic Surface, Expansion, Molecules, Formalism, Accurate, Solids, State
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:kth:diva-6784DOI: 10.1103/PhysRevB.66.165117ISI: 000179286400053OAI: oai:DiVA.org:kth-6784DiVA: diva2:11593
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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