Hydrides crystal field

The rare earth metals form hydrides readily and a number of studies have been performed on these materials (143). The dihydrides of the rare earths form in CaF2-type structure. The crystal field problem has been applied to characterize the fundamental role of hydrogen in these compounds (144-149). The information accumulated for several dihydrides seems to favor the anionic model, namely, that hydrogen accepts an electron to become negatively charged. We will illustrate the results on PrH2 and ErH2. 

Table 17. Crystal field ground state anticipated on the basis of a first-nearest-neighbor point-charge model for the rare-earth dihydrides. Both hydridic and protonic hydrogen are considered, and the known experimental results are shown. (146).

The experimental results on various NaCl, CsCl, MgCu2 and CuaAu structures described in the article have been extended and improved. Measurements were extended also to the RE-hydrides. Further informations can be found in the Proceedings of the 2nd International Conference on Crystal Field Effects in Metals and Alloys, ed. by A. Furrer, Plenum Press (1977). 

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