First principles calculations of hyperfine parameters on the Ca manganite with substitutional Cd-modeling of a PAC experiment

The APW+loAPW+lo (augmented plane waves+localwaves+local orbitals) method of density functional theory, as implemented in the Wien2k code, is applied to calculate the electric field gradient of manganites. We report the first principles calculations on CaMnO3CaMnO3, and modeling of a perturbed angular correlation experiment with implanted Cd111m isotope. To model the experiment we additionally calculate in Ca1-xCdxMnO3Ca1-xCdxMnO3, where we substitute Cd at the Ca site. Increasing Cd dilution is done with the use of supercells. We find that the experimental CaMnO3CaMnO3 low-temperature value Vzz≈6×10-21V/m2 is reproduced, when optimizing internal parameters. The analysis of the EFG tensor at the Ca atoms, with different electric field gradients at inequivalent positions, reveals that the convergence of the calculations is obtained.