Neutron powder diffraction studies, hydrogen

Wijeyesekera, S. D. Corbett, J. D. (1985). A Neutron Powder Diffraction Study of Zirconium Bromide Deuteride, ZrBrD. Two Hydrogen Atoms in the Same Metal Interstice, Solid State Common. 54, 657 - 660. 

INS studies of D2 adsorption on HKUST-1 were consistent with previous neutron powder diffraction studies. The results showed that there were three binding sites for hydrogen loading <2.0 H2 Cu and these sites were progressively populated with increased loading. The variation of INS peaks with temperature showed that the peak that was populated initially at H2 Cu ratio <0.5 had the highest enthalpy (6-10 kj mol ) while the peaks corresponding to the other sites had lower enthalpies. 

The crystalline structure of 2-nitroguanidine had already been previously studied by Bryden and coworkers1 (Ref. 29 therein). They there report the existence, but not the position, of hydrogen bonds, which was instead rendered possible through the use of the neutron powder diffraction method5. The skeleton backbone of this molecule consisting of a central C atom and four N atoms is almost coplanar. Both nitramine groups are essentially on the plane of the molecular skeleton. 

Spectroscopic techniques nicely compliment synthesis and capacity work. One paper reviewed recent work on neutron powder diffraction, where MOFs loaded with different deuterium pressure were studied to directly pin point the location of hydrogen in these porous systems. For the first time the absorbed hydrogen molecules were located in the organic linker, and this highlights then-importance. It would be interesting to test this approach on the other systems that store weakly bound hydrogen. 

Studies of hydrogen adsorption on Cu3[Co(CN)6]2 using high-resolution neutron powder diffraction showed that at 1,2 and 2.3 H2/CU loadings, the hydrogen was absorbed on two sites. The strongest adsorption site was an interstitial location within the structure. The second adsorption site was associated with exposed Cu ion coordination sites that result from the presence of [ColCN) ] vacancies. 

NiII0 6 (aQ = 3.72 A). A powder neutron diffraction study (20) of this interstitial compound showed the hydrogen atoms to occupy only octahedral sites of the fee nickel lattice. 

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