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

Ricardo P. Moreira; E. Lora da Silva; Gonçalo N. P. Oliveira; Pedro Rocha-Rodrigues; Alessandro Stroppa; Claire V. Colin; Céline Darie; João G. Correia; Lucy V. C. Assali; Helena M. Petrilli; Armandina M. L. Lopes; João P. Araújo

arXiv · 2407.21749

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

Ricardo P. Moreira·E. Lora da Silva·Gonçalo N. P. Oliveira·Pedro Rocha-Rodrigues·Alessandro Stroppa·Claire V. Colin·Céline Darie·João G. Correia·Lucy V. C. Assali·Helena M. Petrilli·Armandina M. L. Lopes·João P. Araújo

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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 $ab-initio$ 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 $3d$-states. By considering $U_{eff}$=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.

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Ricardo P. Moreira, E. Lora da Silva, Gonçalo N. P. Oliveira, Pedro Rocha-Rodrigues, Alessandro Stroppa, Claire V. Colin, Céline Darie, João G. Correia, Lucy V. C. Assali, Helena M. Petrilli, Armandina M. L. Lopes, João P. Araújo. 2025-09-10. Ge-based Clinopyroxene series: first principles and experimental local probe study. https://arxiv.org/abs/2407.21749

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