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Thermodynamics of ordered and disordered phases in the binary Mo-Ru system
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
CALPHAD, Brookline, Massachusetts, USA.
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
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2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 18, 184203- p.Article in journal (Refereed) Published
Abstract [en]

Wehave performed ab initio calculations of the mixing enthalpy forthe Mo-Ru alloy system. Both completely random alloys on thefcc, bcc, and hcp lattices as well as ordered andpartially ordered structures based on the hcp lattice and a phase have been examined. Further, we have performed aground-state search for the Ru-rich region using ab initio derivedeffective interactions, and find a series of structures below thetie line of the simple compounds. Using the structures fromthis ground-state search, we are able to make an estimationof the contribution to the total energy due to orderingeffects in this system. We find unusually large deviations betweencalculated and experimental values of the mixing enthalpy for Ru-richhcp alloys. Our calculations indicate, in agreement with experiment, thatthere are ordering trends in the system. However, even underassumption of maximal order theoretical results differ substantially from theexperiment. Possible reasons for the disagreement are discussed.

Place, publisher, year, edition, pages
2007. Vol. 75, no 18, 184203- p.
Keyword [en]
molybdenum alloys, ruthenium alloys, ab initio calculations, enthalpy, ground states, total energy
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-14273DOI: 10.1103/PhysRevB.75.184203OAI: oai:DiVA.org:liu-14273DiVA: diva2:23067
Available from: 2007-02-01 Created: 2007-02-01 Last updated: 2017-12-13
In thesis
1. Development and application of Muffin-Tin Orbital based Green’s function techniques to systems with magnetic and chemical disorder
Open this publication in new window or tab >>Development and application of Muffin-Tin Orbital based Green’s function techniques to systems with magnetic and chemical disorder
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Accurate electronic structure calculations are becoming more and more important because of the increasing need for information about systems which are hard to perform experiments on. Databases compiled from theoretical results are also being used more than ever for applications, and the reliability of the theoretical methods are of utmost importance. In this thesis, the present limits on theoretical alloy calculations are investigated and improvements on the methods are presented.

A short introduction to electronic structure theory is included as well as a chapter on Density Functional Theory, which is the underlying method behind all calculations presented in the accompanying papers. Multiple Scattering Theory is also discussed, both in more general terms as well as how it is used in the methods employed to solve the electronic structure problem. One of the methods, the Exact Muffin-Tin Orbital method, is described extensively, with special emphasis on the slope matrix, which energy dependence is investigated together with possible ways to parameterize this dependence.

Furthermore, a chapter which discusses different ways to perform calculations for disordered systems is presented, including a description of the Coherent Potential Approximation and the Screened Generalized Perturbation Method. A comparison between the Exact Muffin-Tin Orbital method and the Projector Augmented-Wave method in the case of systems exhibiting both compositional and magnetic disordered is included as well as a case study of the MoRu alloy, where the theoretical and experimental discrepancies are discussed.

The thesis is concluded with a short discussion on magnetism, with emphasis on its computational aspects. I further discuss a generalized Heisenberg model and its applications, especially to fcc Fe, and also present an investigation of the competing magnetic structures of FeNi alloys at different concentrations, where both collinear and non-collinear magnetic structures are included. For Invar-concentrations, a spin-flip transition is found and discussed. Lastly, I discuss so-called quantum corrals and possible ways of calculating properties, especially non-collinear magnetism, of such systems within perturbation theory using the force theorem and the Lloyd’s formula.

Place, publisher, year, edition, pages
Institutionen för fysik, kemi och biologi, 2006
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1063
Keyword
Mathematical physics, Theoretical Physics, Muffin-Tin Orbital method, Calculations, Magnetism, Lloyd’s formula
National Category
Other Physics Topics
Identifiers
urn:nbn:se:liu:diva-8231 (URN)91-85643-28-9 (ISBN)
Public defence
2006-12-15, Planck, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2007-02-01 Created: 2007-02-01 Last updated: 2009-03-04

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Kissavos, Andreas E.Shallcross, SamGrånäs, OscarAbrikosov, Igor A.

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