The amorphous phase of bismuth silicate (${\mathrm{Bi}}_2{\mathrm{SiO}}_5$) is characterized by an exceptionally large dielectric permittivity over a wide temperature range. This study explores the relationship between this remarkable property and the material's atomic-scale structure, which has been modeled from experimental x-ray and neutron scattering as well as x-ray absorption fine structure and nuclear magnetic resonance spectroscopy data in a reverse Monte-Carlo approach. The resulting structural model is analyzed to reveal short- and intermediate-range features on the atomic scale. Our results show that the exceptional dielectric performance stems from the asymmetric coordination of $\mathrm{Bi}\text{−}{\mathrm{O}}_x$ polyhedra as well as a nanosegregation induced by ${\mathrm{SiO}}_4$ chains, which together boost local polarizability. These findings establish a direct link between disordered atomic structures and enhanced dielectric properties, and set a clear benchmark for amorphous materials.

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• Atomic & molecular structure
• Dielectric properties
• Amorphous materials
• Atom diffraction
• Monte Carlo methods