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Investigation of th...
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Nedumkandathil, RejiStockholms universitet,Institutionen för material- och miljökemi (MMK),Stockholm University
(author)
Investigation of the Order–Disorder Rotator Phase Transition in KSiH3 and RbSiH3
- Article/chapterEnglish2017
Publisher, publication year, extent ...
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2017-02-24
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American Chemical Society (ACS),2017
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printrdacarrier
Numbers
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LIBRIS-ID:oai:DiVA.org:su-141587
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https://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141587URI
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https://doi.org/10.1021/acs.jpcc.6b12902DOI
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https://research.chalmers.se/publication/249099URI
Supplementary language notes
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Language:English
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Summary in:English
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Subject category:ref swepub-contenttype
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Subject category:art swepub-publicationtype
Notes
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The β–α (order–disorder) transition in the silanides ASiH3 (A = K, Rb) was investigated by multiple techniques, including neutron powder diffraction (NPD, on the corresponding deuterides), Raman spectroscopy, heat capacity (Cp), solid-state 2H NMR spectroscopy, and quasi-elastic neutron scattering (QENS). The crystal structure of α-ASiH3 corresponds to a NaCl-type arrangement of alkali metal ions and randomly oriented, pyramidal, SiH3– moieties. At temperatures below 200 K ASiH3 exist as hydrogen-ordered (β) forms. Upon heating the transition occurs at 279(3) and 300(3) K for RbSiH3 and KSiH3, respectively. The transition is accompanied by a large molar volume increase of about 14%. The Cp(T) behavior is characteristic of a rotator phase transition by increasing anomalously above 120 K and displaying a discontinuous drop at the transition temperature. Pronounced anharmonicity above 200 K, mirroring the breakdown of constraints on SiH3– rotation, is also seen in the evolution of atomic displacement parameters and the broadening and eventual disappearance of libration modes in the Raman spectra. In α-ASiH3, the SiH3– anions undergo rotational diffusion with average relaxation times of 0.2–0.3 ps between successive H jumps. The first-order reconstructive phase transition is characterized by a large hysteresis (20–40 K). 2H NMR revealed that the α-form can coexist, presumably as 2–4 nm (sub-Bragg) sized domains, with the β-phase below the phase transition temperatures established from Cp measurements. The reorientational mobility of H atoms in undercooled α-phase is reduced, with relaxation times on the order of picoseconds. The occurrence of rotator phases α-ASiH3 near room temperature and the presence of dynamical disorder even in the low-temperature β-phases imply that SiH3– ions are only weakly coordinated in an environment of A+ cations. The orientational flexibility of SiH3– can be attributed to the simultaneous presence of a lone pair and (weakly) hydridic hydrogen ligands, leading to an ambidentate coordination behavior toward metal cations.
Subject headings and genre
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Jaworski, AleksanderStockholms universitet,Institutionen för material- och miljökemi (MMK),Stockholm University(Swepub:su)ajawo
(author)
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Fischer, AndreasUniversität Augsburg,University of Augsburg
(author)
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Österberg, Carin,1987Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)ocarin
(author)
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Lin, Yuan-Chih,1987Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)yuanchih
(author)
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Karlsson, Maths,1978Chalmers tekniska högskola,Chalmers University of Technology(Swepub:cth)maths
(author)
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Grins, JekabsStockholms universitet,Institutionen för material- och miljökemi (MMK),Stockholm University(Swepub:su)mat
(author)
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Pell, Andrew J.Stockholms universitet,Institutionen för material- och miljökemi (MMK)(Swepub:su)apell
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Edén, MattiasStockholms universitet,Institutionen för material- och miljökemi (MMK),Stockholm University(Swepub:su)eden
(author)
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Häussermann, UlrichStockholms universitet,Institutionen för material- och miljökemi (MMK),Stockholm University(Swepub:su)ulrich
(author)
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Stockholms universitetInstitutionen för material- och miljökemi (MMK)
(creator_code:org_t)
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In:The Journal of Physical Chemistry C: American Chemical Society (ACS)121:9, s. 5241-52521932-74471932-7455
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