 compared to the thermal fluctuation of Kohn-Sham states for disordered systems at room temperature. For a heuristic theory, see [@prasai2016eph]), the DC conductivity of metallic models are of the order of $10^{2}~\Omega^{-1}cm^{-1}$ at both concentrations. For the insulating model at $x$=0.15, this value is of order $10^{-6}~\Omega^{-1}cm^{-1}$ whereas for insulating model at $x$=0.25, this value is lower but can not be ascertained from our calculations. We find that the metallized models show, at least, $\sim 10^8$ times higher conductivity than the insulating models. The computed conductivity for metallic models are comparable to the DC conductivity values of liquid silicon ($\approx 10^4~\Omega^{-1}cm^{-1}$, [@glazov]).

![(a) Optical conductivity of insulating (black curve) and metallized (red curve) models for (GeSe$_3$)$_{0.75}$Ag$_{0.25}$ model computed using Kubo-Greenwood Formula (KGF). Brillouin zone sampling is done over 4 k-points. Average over 3 directions was taken to eliminate artificial anisotropy. (b) DC conductivity as a function of Gaussian approximant $\delta$E. black squares: insulating model at $x$=015, red triangles: metallic model at $x$=0.15, green diamonds: insulating model at $x$=0.25, blue circles: metallic model at $x$=0.25[]{data-label="fig4"}](KGF.eps){width="\linewidth"}

We track the atomic rearrangements associated with the metallization of network to identify the microscopic origin of metallicity. Recalling that these are inhomogenous glasses with phase separation into Ag-rich [*a-*]{}Ag$_2$Se phase and residual Ge-Se backbone, we note that the insulator-metal transition in these glasses can be viewed in terms of relative ratio of these two competing phases. In particular, we make the following three observations associated with the insulator-metal transition: i) Growth of Ag-Se phase, ii) Depletion of tetrahedral GeSe$_2$ phase, and iii) Growth of Ge-rich phase in host network. Below we briefly comment on these three observations, a more detailed account of structural rearran