The electronic structure of Hf2Co:: perturbed angular correlation study and first principle calculations

The results of high resolution TDPAC measurements of electric quadrupole interaction (EQI) at the Ta-181 probe ion in the polycrystalline intermetallic compound Hf2Co of the Ti2Ni structure type, in a temperature range from 77 to 1200 K, are presented. The results show the presence of two independent EQIs. At room temperature their frequencies are omegaQ(1) = 36(3) Mrad s(-1) at the 16c, and omega(Q2) = 230(3) Mrad s(-1) at the 48f position. The low frequency interaction is characterized by an unusual temperature dependence which shows a pronounced maximum. The temperature dependence of all relevant physical parameters (the electric field gradient (EFG) principal component V-ZZ, the EFG distribution parameter 6, the asymmetry parameter eta, and the fractions of ions contributing to the specific interaction) are also presented. In addition, the EFG parameters of the same structure are calculated using the full-potential linearized augmented plane-wave (FP-LAPW) method as implemented in the WIEN97 package, and the results are compared with the measured data and some previous calculations obtained using the full-potential linear muffin-tin orbital (FP-LMTO) method in the atomic sphere approximation (ASA).