  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.
