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We use the linear muffin-tin orbital formalism, in the atomic sphere approximation, to obtain the electric field gradient (EFG) at the nucleus for metallic Zr and Hf, in the HCP structure. Combined corrections are included in the calculations. To evaluate the importance of relativistic effects, non-relativistic and scalar relativistic calculations were performed. In agreement with experiment, we find that the EFG for Hf is larger than for Zr by a factor of more than 2. We show that this is mainly due to the behaviour of metallic p and d orbitals, which for Hf have comparatively larger values close to the nuclear region. Because Hf and Zr are in the same group of the periodic table, Hf is often used as a probe in perturbed angular correlation experiments, when investigating the EFG for Zr alloys. We use our results to note that, for similar values of orbital occupations, the EFG at a Hf probe is larger than the EFG at a Zr atom placed at the same site.

We have used a first-principles real-space approach to investigate the electronic structure and the magnetic behavior of interstitial Fe impurities in divalent Ca, Sr, and Yb hosts. The dependence of the local moment as a function of lattice relaxation around the impurity is obtained and contrasted with that of interstitial Fe in trivalent and tetravalent Zr, Y, Ti, and Sc hosts. The trends obtained for local moment formation at the impurity site are in agreement with experimental time-differential perturbed ␥-ray angular distribution technique observations.