Perturbed angular correlation studies of chemically generated electric field gradients in Hf compounds

Abstract

The time-differential-perturbed-angular-correlation (TDPAC) technique has been applied to the study of electric quadrupole interactions in HfO2, HfO(H2PO4) ⋅H2O, and HfP2O7. Strong perturbations were seen in each case, with time evolution characteristic of the static electric field gradients generated by the electron distributions in chemical bonds. Analysis of the experimental data within a theoretical framework has permitted derivation of the electric field gradient parameters associated with the Hf–O bonds in the oxide and the two phosphate compounds. A simple model calculation involving orbital populations appears capable of reproducing the experimental results and provides insight into the bonding features of these relatively complex, but structurally known, systems. The TDPAC signature of each compound appears sufficiently unique so as to offer the possibility of its adaptation as a microscopic probe of more complicated or unknown crystalline and liquid systems.