Kohlmann, Holger and Kurtzemann, Nadine and Weihrich, Richard and Hansen, Thomas (2009) In situ Neutron Powder Diffraction on Intermediate Hydrides of MgPd3 in a Novel Sapphire Gas Pressure Cell. ZEITSCHRIFT FUR ANORGANISCHE UND ALLGEMEINE CHEMIE, 635 (15). pp. 2399-2405. ISSN 0044-2313,
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A novel gas pressure cell for in situ neutron powder diffraction has been developed. It is based oil a single crystal sapphire tube as a sample holder, allows a 360 degrees unobstructed access by the neutron beam and has little background contribution. This device was used to study the hydrogenation of alpha-MgPd3, Which undergoes a hydrogen driven rearrangement from a ZrAl3 to a AuCu3 type structure. Deuterium could be located and a strong preference of [Pd-6] voids was found in alpha-MgPd3D0.79 under 5 bar and in alpha-MgPd3D0.94 under 20 bar deuterium pressure. The crystal structure may be described as a new defect Superstructure variant of the NaCl type. In situ thermal analysis under 5 bar hydrogen pressure showed that both the hydrogen uptake of alpha-MgPd3, Which is complete at temperatures below 450 K, and the transformation to the hydride of cubic beta-MgPd3, starting around 550 K, are exothermic. This completion of the hydrogenation-dehydrogenation series of MgPd3 suggests, that the rearrangement of the metal structure proceeds by a hydrogen assisted gliding mechanism with a shift vector of 1/2[110]. This is also supported by quantum chemical calculations, which show a decohesion of the intermetallic structure upon hydrogenation accompanied by the appearance of Pd-H bonding interactions.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | CRYSTAL-STRUCTURES; METAL-HYDRIDES; HYDROGEN; SCATTERING; ALLOYS; MAGNETISM; HDDR; In situ techniques; Neutron diffraction; Metal hydrides; Intermetallic phases; Hydrogenation |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Anorganische Chemie > Arbeitskreis Dr. Richard Weihrich |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 14 Oct 2020 06:36 |
| Last Modified: | 14 Oct 2020 06:36 |
| URI: | https://pred.uni-regensburg.de/id/eprint/29902 |
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