Ge-based Clinopyroxene series: first principles and experimental local probe study

Ricardo P. Moreira; E. Lora da Silva; GonÃ§alo N. P. Oliveira; Pedro Rocha-Rodrigues; Alessandro Stroppa; Claire V. Colin; CÃ©line Darie; JoÃ£o G. Correia; Lucy V. C. Assali; Helena M. Petrilli; Armandina M. L. Lopes; JoÃ£o P. AraÃºjo

paper

Ge-based Clinopyroxene series: first principles and experimental local probe study

arXiv:2407.21749

Abstract

The structural and electronic properties of the CaMnGe $_{2}$ O $_{6}$ and SrMnGe $_{2}$ O $_{6}$ clinopyroxene systems have been investigated by means of perturbed angular correlation (PAC) measurements, performed at ISOLDE, combined with $ab - ini t i o$ electronic structure calculations within the density functional theory (DFT) framework. The partial density of states (PDOS) of the CaMnGe $_{2}$ O $_{6}$ and SrMnGe $_{2}$ O $_{6}$ 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 $3 d$ -states. By considering $U_{e f f}$ =4 eV, we obtained a band gap width of 1.82 eV and 1.70 eV, for the CaMnGe $_{2}$ O $_{6}$ and SrMnGe $_{2}$ O $_{6}$ , 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.