A PERTURBED-ANGULAR-CORRELATION STUDY OF THE ELECTRIC-FIELD GRADIENT AT THE IN SITE IN COMPOUNDS OF THE HG-IN ALLOY SYSTEM

The electric-field gradient (EFG) of dilute Cd-111 nuclei in compounds of the Hg-In alloy system has been investigated by perturbed angular correlation (PAC) measurements of the electric quadrupole interaction (QI) of Cd-111 on In sites. It has been found that, as in the pure met als Hg and In, the quadrupole frequency decreases with increasing temp erature according to the relation nu(q)(T) = nu(q)(0)(1 - BT3/2). The strength constant B in the intermetallic phases, however, is up to 35% smaller than in the pure metals. The QI parameters are consistent wit h an orthorhombic gamma-Pu-type lattice for beta-Hg (Hg80In20), but ar e difficult to reconcile with the structures proposed for HgIn. An int ermetallic compound HgIn2 has not been observed.