Effect on Hyperfine Interactions (HFI) parameters in presence of point-defects made out of oxygen vacancies and or Tantalum (Ta) substitutions at the Hafnium (Hf) site in the monoclinic hafnia (m-HfO \(_2\) ) is proposed. The scope of the study is to better understand the microscopic origin of the nuclear quadrupole character (i.e., local crystal structure and dynamics of lattices) in m-HfO \(_2\) through the systematic computational study of HFI parameters. Thus, an attempt based on the first-principles electronic structure calculations and on-site Hubbard U (self-consistent, \(U_{self}\) ) is proposed herein, to evaluate the correlation of dipolar effects (spin-spin and spin-nuclear interactions) on the estimated electric quadrupolar parameters, so called HFI parameters of the host and probe nuclei in m-HfO \(_2\) . The measure of quadropolar parameters through the calculations of electric-field gradient (EFG) and associated asymmetric, \(\eta\) and quadrupole frequencies, \(\omega _Q\) are thus, undertaken in this study in the pristine and also point-defects (single Ta substitution at Hf-site and oxygen vacancy) included m-HfO \(_2\) . Charged ( \(q = +1\) ) or neutral ( \(q = 0\) ) point-defects induced additional dipole-dipole interactions, play a critical role in the estimation of the EFG component, \(V_{zz}\) at the metal sites pertaining to the singlet or triplet spin-centre in the host m-HfO \(_2\) . Our results are discussed in comparison with the known Time Differential Perturbed Angular Correlation (TDPAC) data. Observations from the spin-densities and electronic structure modulation due to point-defects are crucial to explain anomalies of the current estimated and earlier known \(V_{zz}\) at the Ta-probe site from TDPAC measurements in reference to the host lattice Hf-sites. Spin-orbital effects are marginal on the estimated HFI parameters. The observation of spin-spin and spin-nuclear interactions in current binary oxide through HFI parameters determination may provide a rational implication in structural dynamics for other similar oxides.
