STRUCTURAL STUDY OF YMN2 HYDRIDES

Structural properties of YMn2Hx (0 less than or equal to x less than o r equal to 4.3) were studied. It was established by means of X-ray dif fraction that at 300 K the lattice parameter increases continuously up on hydrogen absorption, and the cubic crystal structure remains preser ved up to x=3.5. For the fully charged YMn2H4.3, a rhombohedral distor tion was found (space group R-3m). The extended X-ray absorption, fine structure (EXAFS) method was used to study local order at both room a nd low temperatures. It was found that hydrides with x=1 and 2 are loc ally highly disordered.