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Geometry of the Valence Transition Induced Surface Reconstruction of Sm(0001)
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2002 (English)In: Physical Review Letters, ISSN 0031-9007, Vol. 88, no 13, 136102- p.Article in journal (Refereed) Published
Abstract [en]

We present a structural determination of the surface reconstruction of the Sm(0001) surface using surface x-ray diffraction, scanning tunneling microscopy, and ab initiocalculations. The reconstruction is associated with a large (22%) expansion of the atomic radius for the top monolayer surface Sm atoms. The mechanism driving the surface reconstruction in Sm is unique among all elements and is connected to the strong correlations of the 4f electrons in Sm and the intermediate valence observed in certain Sm compounds. The atoms constituting the top monolayer of Sm(0001) have vastly different chemical properties compared to the layer underneath and behave as if they were an adsorbate of a different chemical species.

Place, publisher, year, edition, pages
2002. Vol. 88, no 13, 136102- p.
National Category
Natural Sciences
URN: urn:nbn:se:uu:diva-92688DOI: 10.1103/PhysRevLett.88.136102OAI: oai:DiVA.org:uu-92688DiVA: diva2:165859
Available from: 2005-03-10 Created: 2005-03-10 Last updated: 2012-04-01Bibliographically approved
In thesis
1. Theoretical Studies of Two-Dimensional Magnetism and Chemical Bonding
Open this publication in new window or tab >>Theoretical Studies of Two-Dimensional Magnetism and Chemical Bonding
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis is divided into two parts. In the first part we study thermodynamics of the two-dimensional Heisenberg ferromagnet with dipolar interaction. This interaction breaks the conditions of the Mermin-Wagner theorem, resulting in a finite transition temperature. Our calculations are done within the framework of the self-consistent spin-wave theory (SSWT), which is modified in order to include the dipolar interaction. Both quantum and classical versions of the Heisenberg model are considered.

The second part of the thesis investigates the chemical bonding in solids from the first principles calculations. A new chemical bonding indicator called balanced crystal orbital overlap population (BCOOP) is developed. BCOOP is less basis set dependent than the earlier indicators and it can be used with full-potential density-functional theory (DFT) codes. We apply BCOOP formalism to the chemical bonding in the high-T_c superconductor MgB2 and the theoretically predicted MAX phase Nb3SiC2. We also study how the chemical bonding results in a repulsive hydrogen–hydrogen interaction in metal hydrides. The role of this interaction in the structural phase transition in Ti3SnHx is investigated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2005. vii + 87 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 21
Physics, spin Hamiltonians, quantized spin models, Heisenberg model, spin waves, self-consistent spin-wave theory, dipolar interaction, density functional theory, chemical bonding, overlap population, MAX phases, metal hydrides, Fysik
National Category
Physical Sciences
urn:nbn:se:uu:diva-4815 (URN)91-554-6164-6 (ISBN)
Public defence
2005-04-01, Siegbahnsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 10:15
Available from: 2005-03-10 Created: 2005-03-10Bibliographically approved

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Delin, AnnaEriksson, Olle
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