Abstract
Electric-field gradients have been measured in the isostructural intermetallic compounds Zr4Al3 and Hf4Al3, using radioactive 181Hf/181Ta hyperfine probes. In both compounds, two well-defined electric-field gradients have been observed, whose temperature dependence follows the T3/2 rule in the temperature range 30–1170 K. Using the full-potential augmented plane-wave + local-orbitals formalism, the electric-field gradients have been calculated. On the basis of the 181Ta hyperfine interaction parameters, the possible Hf/Zr lattice sites have been assigned. In this way the controversy concerning the lattice structure of these compounds deduced from X-ray diffraction has been solved.