Deuterium site occupation in the oxygen-stabilized η-carbides Zr3V3ODx. II. Application of a geometric model

Abstract

A geometric model has been applied to the η‐carbides Zr₃V₃OD_x, which belong to space group Fd3m. With criteria of minimum hole size and minimum distance between deuterium atoms and with the assumption that the larger interstices are preferred, it was possible to rationalize the experimentally observed preference, in decreasing order, for 32e sites, 192i sites, 96g₁, and 96g₂ sites. The respective numbers of coordinating metal atoms for these interstices are Zr₃V, Zr₂V₂, Zr₃V, and ZrV₃. The largest interstices, which are the octahedral 8a sites with Zr₆ coordination, remain empty for x=1.86, 2.85, and 4.93 because of their proximity to the more numerous 32e sites. The failure of deuterium atoms to occupy any 96g₁ (Zr₃V) sites at x=1.86 may indicate the existence of a short‐range repulsive interaction between oxygen and deuterium. The possibilities for achieving higher values of x are also explored.