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Due to technical constraints this correction was published in volume 240:1 with erroneous article citation ID number 9 whereas this should have been 79 which is corrected as such. Springer Nature sincerely apologizes towards the author(s) for the inconvenience caused. [ABSTRACT FROM AUTHOR]

The present Time Differential Perturbed γ-γ Angular Correlation (TDPAC) measurements in bulk HfO2 report, for the first time, the presence of three regular sites at ambient condition, apart from the stable monoclinic phase (m-HfO2). Also, the effects of Gd impurity (5 at%) on HfO2 crystal structure was investigated by PAC. In pure HfO2, apart from the monoclinic component (~76%), four other minor frequency components have been found at room temperature. To further investigate the origin of these minor frequency components, PAC measurement at 673 K was performed. At 673 K, population of two of the four minor components was enhanced at the expense of the m-HfO2 as the population of m-HfO2 reduces to ~58%. On doping with 5 at% Gd, the population of monoclinic site drastically reduced to ~10% while one of the minor components got enhanced to a large extent (68%). The enhancements of the three minor components, both by temperature or by Gd impurity, indicate that these are the regular phases of HfO2 and could therefore be attributed to three orthorhombic phases of HfO2. The fourth minor component (5–10%) with values of ωQ ~ 7 Mrad/s, η = 0 can be assigned to crystalline defect site. [ABSTRACT FROM AUTHOR]

Intermetallic compound Zr7Ni10 has been studied by perturbed angular correlation (PAC) spectroscopy to determine the electric field gradient and site occupation of Hf dopant in the compound. A mixture of phase components were found in this sample. The component with Vzz = 6.6(1)× 1021 V/m2 and η = 0.71(1) at room temperature has been assigned to Zr7Ni10 phase. In this sample, Zr2Ni7 and Zr8Ni21 phases were also found to be present along with Zr7Ni10. No phase transition is observed in the temperature range 77-1073 K in this sample. The electric field gradient (Vzz) for Zr7Ni10 phase was found to decrease linearly with temperature. The phase components in Zr7Ni10 have been determined also from X-ray powder diffraction (XRD) measurement. Theoretical calculations of EFG have been performed in Ta-doped Zr7Ni10 using all electron full potential (linearized) augmented plane wave [FP-(L)APW] method, within the framework of the density functional theory (DFT) to compare the results with the values obtained from PAC measurements and to know the site preference of 181Ta probe in the host matrix. [ABSTRACT FROM AUTHOR]