The structural and electronic properties of the CaMnGe2O6 and SrMnGe2O6 clinopyroxene systems have been investigated by means of perturbed angular correlation (PAC) measurements, performed at ISOLDE, combined with ab−initio electronic structure calculations within the density functional theory (DFT) framework. The partial density of states (PDOS) of the CaMnGe2O6 and SrMnGe2O6 stable compounds has been determined, and it has been observed that the requirement of including an on-site Hubbard-U potential was necessary in order to describe the highly correlated Mn 3d-states. By considering Ueff=4 eV, we obtained a band gap width of 1.82 eV and 1.70 eV, for the CaMnGe2O6 and SrMnGe2O6, respectively. Combining electric field gradient (EFG) first principles calculations, using a supercell scheme, with experimental PAC results, we were able to infer that the Cd probe can replace either the A (Ca, Sr) or the Mn sites in the crystalline structures. We also showed that Cd substitution is expected to lead to a reduction in the width of the band gap in these systems, evidencing opportunities for potential band-gap engineering.
@article{arxiv.2407.21749,
title = {Ge-based Clinopyroxene series: first principles and experimental local probe study},
author = {Ricardo P. Moreira and E. Lora da Silva and Gonçalo N. P. Oliveira and Pedro Rocha-Rodrigues and Alessandro Stroppa and Claire V. Colin and Céline Darie and João G. Correia and Lucy V. C. Assali and Helena M. Petrilli and Armandina M. L. Lopes and João P. Araújo},
journal= {arXiv preprint arXiv:2407.21749},
year = {2025}
}