Explaining an anomalous pressure dependence of shear modulus in germanate glasses based on Reverse Monte Carlo modelling

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  • Søren S. Sørensen
  • Xuan Ge
  • Matthieu Micoulaut
  • Ying Shi
  • Mikkel Juelsholt
  • Jensen, Kirsten Marie Ørnsbjerg
  • Jörg Neuefeind
  • Lars R. Jensen
  • Michal Bockowski
  • Morten M. Smedskjaer
Unlike traditional silicate glasses, germanate glasses often feature non-monotonic variations in material properties (e.g., elastic moduli and glass transition temperature) with varying chemical composition, temperature, and pressure. However, the underlying atomic-scale structural origins remain poorly understood. This is because, in most oxide glasses, the structural changes are quantified through solid-state NMR spectroscopy, but unfortunately the only NMR active germanium isotope (73Ge) has very unfavorable NMR properties. Here, we circumvent this problem by using high-energy X-ray and neutron total scattering coupled with ab initio molecular dynamics simulations as input for Reverse Monte Carlo modeling. In detail, we study the structure and properties of two sodium germanate glasses (10Na2O-90GeO2 and 20Na2O-80GeO2) subjected to permanent densification through hot compression up to 2 GPa at the glass transition temperature. While density as well as Young's and bulk modulus increase with pressure as expected, shear modulus first increases and then decreases slightly at higher pressures. The refined atomistic structure models suggest that the glasses feature a distribution of 4, 5, and 6 coordinated Ge with a majority of 4 and 5 coordinated species. Only minor changes in the Ge–O coordination occur upon hot compression, but a notable transformation of edge- to corner-sharing Ge-polyhedra is found. This anomalous polyhedral packing causes a lower number of angular constraints upon higher pressure treatment, explaining the non-monotonic trend of shear modulus with pressure. We also find that the rings become smaller and less circular upon compression, contributing to the volumetric compaction. These findings may aid the future design of germanate glasses with tailored properties and the general understanding of structure-property relations in oxide glasses.
OriginalsprogEngelsk
TidsskriftJournal of Materials Science and Technology
Vol/bind192
Sider (fra-til)54-64
Antal sider11
ISSN1005-0302
DOI
StatusUdgivet - 2024

Bibliografisk note

Funding Information:
This work was supported by grants from the European Union (ERC, NewGLASS, No. 101044664) and the MSCA Postdoctoral Fellowship (No. 101062110) from the Horizon Europe Framework Programme. Views and opinions expressed are, however, those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. We acknowledge the computational resources supplied by EuroHPC Joint Undertaking with access to Vega at IZUM, Slovenia (No. EHPC-REG-2022R02–224) and Aalborg University (No. CLAAUDIA). Mikkel Juelsholt and Kirsten M. Ø. Jensen are grateful for funding from the Villum Foundation (No. VKR00015416). We also acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. The X-ray total scattering experiments were carried out at beamline P02.1 at PETRA III, and we would like to thank Martin Etter for his assistance in using the beamline. We furthermore thank DANSCATT (supported by the Danish Agency for Science and Higher Education) for support. A portion of this research also used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

Funding Information:
This work was supported by grants from the European Union (ERC, NewGLASS, No. 101044664 ) and the MSCA Postdoctoral Fellowship (No. 101062110 ) from the Horizon Europe Framework Programme. Views and opinions expressed are, however, those of the authors only and do not necessarily reflect those of the European Union or the European Research Council. Neither the European Union nor the granting authority can be held responsible for them. We acknowledge the computational resources supplied by EuroHPC Joint Undertaking with access to Vega at IZUM, Slovenia (No. EHPC-REG-2022R02–224) and Aalborg University (No. CLAAUDIA). Mikkel Juelsholt and Kirsten M. Ø. Jensen are grateful for funding from the Villum Foundation (No. VKR00015416). We also acknowledge DESY (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities. The X-ray total scattering experiments were carried out at beamline P02.1 at PETRA III, and we would like to thank Martin Etter for his assistance in using the beamline. We furthermore thank DANSCATT (supported by the Danish Agency for Science and Higher Education) for support. A portion of this research also used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory.

Publisher Copyright:
© 2024

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