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A critical test of ab initio and CALPHAD methods: The structural energy difference between bcc and hcp molybdenum
Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
Department of Physics, Uppsala University, Uppsala, Sweden.
Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA.
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2005 (English)In: Calphad, ISSN 0364-5916, Vol. 29, no 1, 17-23 p.Article in journal (Refereed) Published
Abstract [en]

Ab initio calculations of the enthalpy of formation of bcc, fcc, and hcp Ru–Mo alloys have been performed for random, ordered, and partially ordered structures. The lattice stability of the bcc and hcp forms of Mo is isolated in order to compare the hcp–bcc difference calculated by ab initio and CALPHAD methods with experimental measurements of the enthalpy of formation of Ru–Mo alloys. The significance of this comparison in calculating the Mo–Ru phase diagram is illustrated. The results of these considerations suggest a rational method for coupling ab initio and CALPHAD techniques might be utilization of the ab initio methods for calculation of the isostructural energies of formation for binary bcc, hcp, and fcc solutions while retaining the CALPHAD lattice stabilities in the calculation of phase diagrams.

Place, publisher, year, edition, pages
2005. Vol. 29, no 1, 17-23 p.
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:liu:diva-14272DOI: 10.1016/j.calphad.2005.04.002OAI: oai:DiVA.org:liu-14272DiVA: diva2:23066
Available from: 2007-02-01 Created: 2007-02-01
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, SamAbrikosov, Igor A.

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