| Popis: |
Based on Rietveld analysis of powder neutron diffraction data, the deuterium atoms in Be 2 ZrD 1.5 are found at 298 K to occupy trigonal bipyramidal sites. In the AlB 2 type structure, two tetrahedral and one trigonal bipyramidal sites are closely located and can only be occupied by one deuterium atom. The coordination found at 298 K may represent an average of deuterium atoms occupying all the three mentioned positions, which is indicated by a large displacement factor. At low temperatures, T 2 type structure in space group P6/mmm , showed significant improvement for the model where deuterium solely occupies tetrahedral sites. The results indicate a continuous transition from a (partly) ordered structure at T = 12 K with deuterium in tetrahedral sites, to a disordered structure with deuterium, in average, filling the trigonal bipyramidal sites at 298 K. |
Full Text from ScienceDirect