Extended Czjzek model applied to NMR parameter distributions in sodium metaphosphate glass

TL;DR

This paper applies the Extended Czjzek Model to analyze NMR parameter distributions in sodium metaphosphate glass, combining MD simulations, DFT calculations, and experimental data to enhance understanding of disordered structures.

Contribution

The study introduces the application of the Extended Czjzek Model to NMR parameter distributions in a glass system, integrating computational and experimental approaches for structural insights.

Findings

ECM effectively describes NMR parameter distributions in sodium metaphosphate glass.

Theoretical NMR parameters agree well with experimental data, validating the structural model.

ECM provides new insights into the structural characterization of disordered systems.

Abstract

The Extended Czjzek Model (ECM) is applied to the distribution of NMR parameters of a simple glass model (sodium metaphosphate, $\mathrm{NaPO_3}$) obtained by Molecular Dynamics (MD) simulations. Accurate NMR tensors, Electric Field Gradient (EFG) and Chemical Shift Anisotropy (CSA), are calculated from Density Functional Theory (DFT) within the well-established PAW/GIPAW framework. Theoretical results are compared to experimental high-resolution solid-state NMR data and are used to validate the considered structural model. The distributions of the calculated coupling constant $C_Q\propto |V_{zz}|$ and of the asymmetry parameter $\eta_Q$ that characterize the quadrupolar interaction are discussed in terms of structural considerations with the help of a simple point charge model. Finally, the ECM analysis is shown to be relevant for studying the distribution of CSA tensor parameters and gives new insight into the structural characterization of disordered systems by solid-state NMR.