Hydrogen basal plane

Pandya et al. have used extended X-ray ascription fine structure (EXAFS) to study both cathodically deposited -Ni(OH)2 and chemically prepared / -Ni(OH)2 [44], Measurements were done at both 77 and 297 K. The results for / -Ni(OH)2 are in agreement with the neutron diffraction data [22]. In the case of -Ni(OH)2 they found a contraction in the first Ni-Ni bond distance in the basal plane. The value was 3.13A for / -Ni(OH)2 and 3.08A for a-Ni(OH)2. The fact that a similar significant contraction of 0.05A was seen at both 77 and 297K when using two reference compounds (NiO and / -Ni(OH)2) led them to conclude that the contraction was a real effect and not an artifact due to structural disorder. They speculate that the contraction may be due to hydrogen bonding of OH groups in the brucite planes with intercalated water molecules. These ex-situ results on a - Ni(OH)2 were compared with in-situ results in I mol L"1 KOH. In the ex-situ experiments the a - Ni(OH)2 was prepared electrochemi-cally, washed with water and dried in vac-... 

Hassel and Luzanski obtained quadratic tabular crystals on evaporation of an aqueous solution containing excess hydrogen fluoride. Laue photographs with the incident beam normal to the basal plane showed rhombic symmetry, with, however, appreciable approximation to ditetragonal symmetry. The unit of structure has the dimensions... 

When the nanoclusters are pretreated with atomic hydrogen, a much stronger chemisorbed state of adsorbed thiophene is present. Beam -like structures are observed protruding about 0.4 A above the basal plane in the... 

This result is illustrated with STM line scans, as shown in Fig. 19, where data characterizing the edge of the freshly prepared, fully sulfided structures are compared with a similar line scan for an atomic hydrogen pre-treated cluster. The average height of the edge protrusions shifted down relative to the basal plane by approximately 0.2 A in the hydrogen-treated cluster. This downshift occurs as a... 

Similarly, the much-debated case of FeCo3(CO)i2H has been settled by a low temperature x-ray diffraction study (9) of its derivative, FeCo3-(CO)9[P(OMe)3]3H, and has been confirmed recently by neutron diffraction (10). This study shows that the hydrogen is under the basal plane. 

Hexagonal AB5 compounds form orthorhombic hydrides. Basal plane expansion, caused by hydrogen occupation of interstitial sites (4), change the compound s structure and can be ordered or disordered. For example, Kuijpers and Loopstra (4) found, by neutron diffraction, that the deuterium atoms in PrCo5D4 were ordered on certain interstitial octahedral and tetrahedral sites. The sites occupied by hydrogen in various AB5 hydrides are not fully understood because of insufficient neutron diffraction data. The available information is considered in the section on configurational entropies. 

Its molecular structure (Figure 37) consists of a centrosymmetric dimer with a bridging H2Al(OR)( U-OR)2Al(OR)H2 entity. The Ta atoms are approximately square pyramidal, with the four phosphorus atoms forming the basal plane (Ta lies 0.64 A out of it). The relatively short Ta—A1 distances are comparable to those found in other transition metal aluminum complexes (Ta—Al 2.79-3.13 A). The hydrogen atoms have not been located, but were evidenced by chemical and spectroscopic techniques (IR 1605, 1540 cm 1 HNMR 16.30p.p.m.). The Ta—(ju-H2)A1 unit is relatively stable, and (54) is inert to carbon monoxide or trimethylamine. It is a poor catalyst in the isomerization of 1-pentene. Formation of complexes analogous to (54) may explain the low yields often obtained from alkoxoaluminohy-drides and metal halides. 

It is noteworthy that the isomerization of cis-2-butene taking place on the edge surface required a hydrogen cocatalyst, but the isomerization of 2-methyl-1-butene on the basal plane occurred in the absence of hydrogen. 

An Electron Energy Loss Spectroscopic Investigation of the Adsorption of Nitric Oxide, Carbon Monoxide, and Hydrogen on the Basal Plane of Ruthenium... 

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