About: Ab initio study of point defects in NiTi-based alloys

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rdf:type	skos:Concept http://linked.opendata.cz/ontology/domain/vavai/Vysledek
Description	Changes in temperature or stress state may induce reversible B2 <-> (R) <-> B19' martensitic transformations and associated shape memory effects in close-to-stoichiometric nickel-titanium (NiTi) alloys. Recent experimental studies confirmed a considerable impact of the hydrogen-rich aging atmosphere on the subsequent B2 austenite <-> B19' martensite transformation path. In this paper, we employ density functional theory to study properties of Ar, He, and H interstitials in B2 austenite and B19' martensite phases. We show that H interstitials exhibit negative formation energies, while Ar and He interstitials yield positive values. Our theoretical analysis of slightly Ni-rich NiTi-based alloys with the austenite B2 structure shows that a slight over-stoichiometry towards Ni-rich compositions in a range 51-52 at.% is energetically favorable. The same conclusion holds for H-doped NiTi with the H content up to approximate to 6 at.%. In agreement with experimental data we predict H atoms to have a strong impact on the martensitic phase transformation in NiTi by altering the mutual thermodynamic stability of the high-temperature cubic B2 and the low-temperature monoclinic B19' phase of NiTi. Hydrogen atoms are predicted to form stable interstitial defects. Changes in temperature or stress state may induce reversible B2 <-> (R) <-> B19' martensitic transformations and associated shape memory effects in close-to-stoichiometric nickel-titanium (NiTi) alloys. Recent experimental studies confirmed a considerable impact of the hydrogen-rich aging atmosphere on the subsequent B2 austenite <-> B19' martensite transformation path. In this paper, we employ density functional theory to study properties of Ar, He, and H interstitials in B2 austenite and B19' martensite phases. We show that H interstitials exhibit negative formation energies, while Ar and He interstitials yield positive values. Our theoretical analysis of slightly Ni-rich NiTi-based alloys with the austenite B2 structure shows that a slight over-stoichiometry towards Ni-rich compositions in a range 51-52 at.% is energetically favorable. The same conclusion holds for H-doped NiTi with the H content up to approximate to 6 at.%. In agreement with experimental data we predict H atoms to have a strong impact on the martensitic phase transformation in NiTi by altering the mutual thermodynamic stability of the high-temperature cubic B2 and the low-temperature monoclinic B19' phase of NiTi. Hydrogen atoms are predicted to form stable interstitial defects. (en)
Title	Ab initio study of point defects in NiTi-based alloys Ab initio study of point defects in NiTi-based alloys (en)
skos:prefLabel	Ab initio study of point defects in NiTi-based alloys Ab initio study of point defects in NiTi-based alloys (en)
skos:notation	RIV/68081723:_____/14:00435504!RIV15-GA0-68081723
http://linked.open...avai/riv/aktivita	I P
http://linked.open...avai/riv/aktivity	I, P(GA106/09/1913)
http://linked.open...iv/cisloPeriodika	1
http://linked.open...vai/riv/dodaniDat	2015
http://linked.open...aciTvurceVysledku	Friák, Martin Dlouhý, Antonín
http://linked.open.../riv/druhVysledku	J - Článek v odborném periodiku
http://linked.open...iv/duvernostUdaju	S - Úplné a pravdivé údaje nepodléhající ochraně podle zvláštních právních předpisů
http://linked.open...titaPredkladatele	Ústav fyziky materiálů AV ČR, v. v. i.
http://linked.open...dnocenehoVysledku	1309
http://linked.open...ai/riv/idVysledku	RIV/68081723:_____/14:00435504
http://linked.open...riv/jazykVysledku	eng - angličtina
http://linked.open.../riv/klicovaSlova	nitinol; shape memory; hydrogen; lattice stability (en)
http://linked.open.../riv/klicoveSlovo	shape memory hydrogen nitinol lattice stability
http://linked.open...odStatuVydavatele	US - Spojené státy americké
http://linked.open...ontrolniKodProRIV	[9DDE646BBE9B]
http://linked.open...i/riv/nazevZdroje	Physical Review. B
http://linked.open...in/vavai/riv/obor	BM
http://linked.open...ichTvurcuVysledku	2 (xsd:int)
http://linked.open...cetTvurcuVysledku	4 (xsd:int)
http://linked.open...vavai/riv/projekt	Martensitic transformations in NiTi alloys
http://linked.open...UplatneniVysledku	2014
http://linked.open...v/svazekPeriodika	89
http://linked.open...iv/tvurceVysledku	Dlouhý, Antonín Friák, Martin Holec, D. Neugebauer, J.
http://linked.open...ain/vavai/riv/wos	000332332300001
issn	1098-0121
number of pages	6 (xsd:int)
http://bibframe.org/vocab/doi	10.1103/PhysRevB.89.014110

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