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Study of optical response in disordered alloys using the generalized recursion in augmented space: Application to ferromagnetic FeCo alloy
2011 (English)In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 406, no 11, p. 2121-2125Article in journal (Refereed) Published
##### Abstract [en]

We propose and briefly describe the generalized recursion in augmented space using a minimal TB-LMTO basis set for the calculation of configuration averaged current response functions in disordered binary alloys. Since disorder in the current terms is off-diagonal and non-separable, single-site mean-field approaches are unable to deal with it without further approximations. The augmented space approach is ideally suited for such situations and the generalized recursion proposed by Viswanath and Muller provides a fast and accurate O(N) technique for the actual calculations of the configuration averaged susceptibilities. We have applied the method to the disordered FeCo alloy. The results agree reasonably well with available experimental data on ordered versions of both the alloy systems, with extra broadening due to disorder induced lifetime effects.

##### Place, publisher, year, edition, pages
2011. Vol. 406, no 11, p. 2121-2125
##### Keywords [en]
Optical properties, Random alloys, FeCo
##### National Category
Metallurgy and Metallic Materials
##### Identifiers
ISI: 000290951200010OAI: oai:DiVA.org:kth-129338DiVA, id: diva2:651746
##### Note

QC 20130927

Available from: 2013-09-27 Created: 2013-09-27 Last updated: 2017-12-06Bibliographically approved
##### In thesis
1. First-principles investigations of ordering in binary alloys
Open this publication in new window or tab >>First-principles investigations of ordering in binary alloys
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
##### Alternative title[en]
978-91-7501-880-5
##### Abstract [en]

The aim of the thesis is to study ordering in binary alloys on the basis of first-principles or {\it ab-initio} techniques employing density functional theory (DFT). The ordering phenomena of materials are of crucial importance for technological applications. The results of the thesis are intended to demonstrate the applicability of the first-principles calculations to provide fundamental insight to the true, namely electronic structure, nature of ordering in binary alloys.

The main part of the thesis focuses on atomic short- and long-range order phenomena in binary alloys as a function of both temperature and chemical composition in FeCo and NiCr alloys. In particular, the influence of magnetism on atomic ordering in FeCo alloys is investigated using the disordered local moment.A large number of concentration dependent effective cluster interactions, derived without the use of any adjustable parameters, are obtained by the SGPM as it is implemented in the EMTO within the CPA. The SGPM interactions can subsequently be used in thermodynamic Monte-Carlo simulations or mean field approximations to determine the ordering phenomena in binary alloys.

First-principles calculations of intrinsic stacking-fault energies (SFE) andanti-phase boundary energies (APBE) in Al$_{3}$Sc and the effects of temperature on SFE and APBE are investigated by using the axial Ising model and supercellapproach. Temperature effects have been taken into consideration byincluding the one-electron thermal excitations in the electronicstructure calculations, and vibrational free energy in the harmonicapproximation as well as by using temperature dependent lattice constants.The latter has been determined within the Debye-Gr{\"u}neisen model,which reproduces well the experimental data.

Within the framework of the quasiharmonic approximation, the thermodynamics and elastic properties of B2- FeCo alloy are studied using first-principles calculations. The calculated thermal and elastic properties are found to be in good agreement withthe available measured values when the generalized gradientapproximations is used for the exchange correlation potential.The calculated finite temperature elastic constants show thatthe FeCo alloy is mechanically stable in the ordered phase.Meanwhile, a large elastic anisotropy exhibits a moderate dependence ontemperature.

##### Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. p. vii, 108
##### Keywords
ordering, random, alloys
##### National Category
Condensed Matter Physics
##### Identifiers
urn:nbn:se:kth:diva-129313 (URN)978-91-7501-880-5 (ISBN)
##### Public defence
2013-10-18, B1, Brinellvagen 23, Materials Science and Engineering, KTH, Stockholm, 10:00 (English)
##### Funder
Swedish Research CouncilEU, European Research Council
##### Note

QC 20130927

Available from: 2013-09-27 Created: 2013-09-26 Last updated: 2013-09-27Bibliographically approved

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##### By author/editor
Rahaman, Moshiour
##### In the same journal
Physica. B, Condensed matter
##### On the subject
Metallurgy and Metallic Materials

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