Revealing the Atomic Structure of Silicate Glasses by Force-Enhanced Atomic Refinement

TL;DR

This paper introduces the FEAR method to accurately determine the atomic structure of sodium silicate glasses, overcoming limitations of traditional simulations and revealing a more ordered medium-range structure than previously thought.

Contribution

The study demonstrates that FEAR provides a more accurate and stable atomic structure of glasses, with better agreement to experimental data and new insights into medium-range order.

Findings

FEAR yields structures with improved experimental data agreement.

FEAR structures are more energetically stable than MD or RMC models.

Reveals a more ordered medium-range structure in sodium silicate glasses.

Abstract

Although experiments can offer some fingerprints of the atomic structure of glasses (coordination numbers, pair distribution function, etc.), atomistic simulations are often required to directly access the structure itself (i.e., the positions of the atoms). On the one hand, molecular dynamics (MD) simulations can be used to generate by quenching a liquid - but MD simulations remain plagued by extremely high cooling rates. On the other hand, reverse Monte Carlo (RMC) modeling bypasses the melt-quenching route - but RMC often yields non-unique glass structures. Here, we adopt the force-enhanced atomic refinement (FEAR) method to overcome these limitations and decipher the atomic structure of a sodium silicate glass. We show that FEAR offers an unprecedented description of the atomic structure of sodium silicate. The FEAR-generated glass structure simultaneously exhibits (i) enhanced agreement with experimental neutron diffraction data and (ii) higher energetic stability as compared to those generated by MD or RMC. This result allows us to reveal new insights into the atomic structure of sodium silicate glasses. Specifically, we show that sodium silicate glasses exhibit a more ordered medium-range order structure than previously suggested by MD simulations. These results pave the way toward an increased ability to accurately describe the atomic structure of glasses.