Structural study of metal–hydrogen interactions in cubic PrH2+x and rare-earth analogues

摘要: Abstract Neutron diffraction data on cubic PrD 2.92 show that the deuterium atoms in octahedral interstices are displaced by 0.31 A from centre towards faces. This leads to a considerable shortening of Pr–D bonds (2.57 as compared 2.74 for position) and thus gain energy. comparison with other RD 2+ x structures (R=La, Ce, Nd) shows displacements R–D decrease atomic size R decreases, whereas shortest contact distances between tetrahedral remain nearly constant (∼2.1 A). These findings suggest one goes light heavy elements (or low high hydrogen contents) energy due R–H bond addition new bonds) is increasingly offset loss repulsive H–H interactions. trend consistent decreased homogeneity range RH phase appearance trigonal 3 systems containing elements.