Electric Quadrupole Interaction in the CdIn2S4 Spinel Compound Studied by111In(111Cd)-PAC: Experiment and Theory

Abstract

Introduction CdIn 2 S 4 is a ternary semiconductor compound crystallizing in the spinel structure. Its optical and electrical properties have been intensively investigated in the past. The results demonstrate peculiar characteristics due to the presence of native defects, the configuration and concentration of which strongly depend on crystal growth conditions and may be varied by subsequent thermal treatments [1].We used the perturbed g±g angular correlation (PAC) method [2] to determine the hyperfine interaction of 111 In( 111 Cd) probe nuclei. The measured electric field gradient (EFG) reflects the local charge distribution including lattice symmetry, defect configurations, different phases and dynamic processes. CdIn 2 S 4 is a unique substance for PAC investigations, since both atoms (In and Cd) of the decaying probe 111 In( 111 Cd) are host atoms of this compound. Moreover, it seems to be the first attempt to study CdIn 2 S 4 by the PAC-method.Modern density functional methods allow to calculate the charge density distribution and the corresponding EFG at different lattice sites from first principles. We applied the WIEN97 program [3], which uses the LAPW-method (full potential linearized augmented plane waves) for the determination of the full potential and the corresponding EFG from a self-consistent charge density distribution. The calculations are performed in elementary cells of a periodic lattice. A particular problem is the EFG at nuclei of impurity atoms, as for instance doping atoms of very low concentrations. This situation corresponds to our 111 Cd-probes, which occupy In-sites because the radioactive precursors are 111 In-atoms. This configuration is also treated by the WIEN97 program.

Electric field gradients in 2H–NbSe2: 93Nb NMR measurements and first-principles calculations

“…This result indicates that EFGs are insensitive to lattice expansion or volume in 2H-NbSe 2 within the range of lattice constants measured [29]. The evolution of EFGs at finite temperatures should be due to the change of orbital occupations, similar to the observations in other multiband systems [31][32][33][34][35][36][37][38][39], which deserves to be further examined carefully in the future.…”