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First-principles study of atomic ordering in fcc Ni-Cr alloys
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Multiscale Materials Modelling.
2014 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 6, p. 064103-Article in journal (Refereed) Published
##### Abstract [en]

We investigate atomic ordering in fcc Ni-rich Ni-Cr alloys using first-principles techniques and statistical mechanics simulations based on the Ising Hamiltonian with effective cluster interactions computed by the screened generalized perturbation method (SGPM) and projector augmented wave (PAW) method. We demonstrate that effective chemical interactions in this system are quite sensitive to alloy composition and in fact to the specific configurational state. The chemical interactions for the high-temperature random state produce the atomic short-range order (SRO) with intensity maximum close to the (2/3 2/3 0) point of the reciprocal space in agreement with the previous first-principles investigation. A consistent with diffuse neutron scattering data maximum at the (1 1/2 0) position is obtained onlywhenwe take into consideration relatively small strain-induced interactions, which solves a long-standing inconsistency between theory and experiment in this system. The calculated transition temperature of order-disorder transition of Ni2Cr alloy, 880 K, is in good agreement with the experimental value of 863 K.

##### Place, publisher, year, edition, pages
2014. Vol. 89, no 6, p. 064103-
##### Keywords [en]
Short-Range Order, Inhomogeneous Electron-Gas, Disordered Binary Alloys, At-Percent Cr, Molecular-Dynamics, Diffuse-Scattering, Lattice-Parameter, Potential Model, Solid-Solution, Monte-Carlo
##### National Category
Metallurgy and Metallic Materials
##### Identifiers
ISI: 000332375400003Scopus ID: 2-s2.0-84894694789OAI: oai:DiVA.org:kth-129342DiVA, id: diva2:651754
##### Funder
Swedish Research Council, 15339-91505-33EU, European Research CouncilVinnova
##### Note

QC 20140331. Updated from manuscript to article in journal.

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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Physical Review B. Condensed Matter and Materials Physics
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Metallurgy and Metallic Materials

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Cite
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