The anelastic spectra of a single crystal of Nb0.9955Zr0.0045, which contained controlled amounts of O and D, were measured in order to clarify the nature of a narrow peak which was due to H tunnelling and which appeared only at the lowest impurity contents in the dilute Nb substitutional alloys. It was shown that the process was due to Zr-D pairs, without any involvement of unwanted O impurities. A saturation of the peak intensity could be explained in terms of increasing interactions among the H atoms, and consequent broadening of the distribution of energy asymmetries in the tunnel system.

H and D Tunnelling Systems in Diluted Nb1-xZrx Alloys. F.Cordero, G.Cannelli, R.Cantelli, F.Trequattrini: Journal of Alloys and Compounds, 1999, 293-295, 338-40