Low-frequency internal friction was measured in monocrystals which had been charged with H at temperatures ranging from 5 to 100K. An internal friction peak was observed at about 60K. The peak appeared under both S44 and S11-S12 shear stress modes. It was suggested that 2 configurations of a Ti-H pair existed simultaneously. One was a 4T configuration in which a H atom formed a tunnel system among 4 tetrahedral interstitial sites in the {100} faces of the cubic cell that contained a Ti atom. The other was a 2T configuration in which a H atom formed a tunnel system between 2 tetrahedral interstitial sites that belonged to 2 neighboring {100} faces of the cubic cell. The internal friction peak was considered to be due to successive jumps of the H atoms between the 2 tunnel systems.

O.Yoshinari, K.Tanaka, H.Matsui: Philosophical Magazine A, 1996, 74[2], 495-507