Electric field gradients created by near neighbour impurity atoms in a cubic silver host

Abstract

The electric quadrupole interactions produced by near neighbour impurity atoms of Cu, Au, Zn, In, Sn and Bi on¹¹¹Cd probe nuclei in a cubic Ag lattice were studied by the TDPAC method. The effects of the type of impurity and its concentration have been investigated. The results show the presence of a high-frequency interactionv ^h_Q superimposed to a smeared out low frequencyv ^l_Q . The high frequency interaction, in the range 20 to 600 MHz, is attributed to impurity atoms located in nearest neighbour sites, while the low frequency interaction, in the range 2 to 12 MHz, is generated by impurities distributed at various different atomic distances from the probe nuclei. Bothv ^h_Q andv ^l_Q increase with impurity concentration leaving the ratiov ^h_Q /v ^l_Q almost constant. The results show that the high frequencyv ^h_Q is linearly dependent on the solute valence, and a logarithmic function of the impurity concentration, in the range 0.5 to 4.5 at. %. Large size effects have been observed in CuAg and BiAg alloys. Instead for ZnAg and SnAg, thev ^h_Q andv ^l_Q variation is attributed basically to charge effects.