Hydrogen short-range order

The major role of TOF-SARS and SARIS is as surface structure analysis teclmiques which are capable of probing the positions of all elements with an accuracy of <0.1 A. They are sensitive to short-range order, i.e. individual interatomic spacings that are <10 A. They provide a direct measure of the interatomic distances in the first and subsurface layers and a measure of surface periodicity in real space. One of its most important applications is the direct determination of hydrogen adsorption sites by recoiling spectrometry [12, 4T ]. Most other surface structure teclmiques do not detect hydrogen, with the possible exception of He atom scattering and vibrational spectroscopy. 

Fig. 1.15 Enlarged view of hydrogen atoms (black circles) in the grain boundary between two grains A and B (gray circles). Note varying short-range order around atoms a and b, which belong to the grain boundary, and fixed order around atoms of type c, which belong to the grain core...

This work is concerned with a further analysis of the short-range order kinetics of hydrogen (H) atoms at tetrahedral interstices in h.c.p. lattice of lutetium (Lu). We compare the results obtained from independent investigation methods for different characteristics—residual electrical resistance [4,5] and heat capacity [6], and reveal the same nature of their conditionality. 

As assumed, the relaxation time corresponds to the time required for the z -type channel migration of hydrogen to change the short-range order parameter value in e times. The temperature dependence of Vh has its usual definition given by a Boltzmann distribution ... 

Jung, P. and Lasser, R. (1992) Short-range ordering of hydrogen isotopes in lutetium, J. Alloys Compounds 190, 25—29. 

Tatarenko, V.A. and Radchenko, T.M. (2002) Kinetics of the hydrogen-isotope short-range ordering in interstitial solid solutions h.c.p.-T -H(D, T), in T.N. Veziroglu et al. (eds.), Hydrogen Materials Science and Chemistry of Metal... 

A similar study has been reported on specifically deuterated pyridines in a series of aqueous solutions. (172) A rotational diffusion model is used to interpret the relaxation data. The diffusion constant for reorientation around the C2 axis of pyridine is found to increase as the viscosity of the solution increases whereas the constant for reorientation about the axis perpendicular fo the molecular plane decreases as the amount of water present in the solution increases. These observations are attributed to short range ordering due to hydrogen bond formation. 

---