  Iron phosphate glasses (IPG) have been proposed as futuristic glass material
for nuclear waste immobilization, anode material for lithium batteries and also
as bioactive glass. In the last decade, there have been attempts to propose
atomistic models of IPG to explain their properties from atomistic viewpoint
and to predict their behavior in radioactive environment. In this paper, we
seek to produce small scale models of IPG that can be handled within the scheme
of Density Functional Theory (DFT) to study the electronic structure of this
material. The starting models generated using Monte Carlo (MC) method [S. Singh
and S. Chandra, Comp. Mat. Sci., 202, 110943, (2022)] were subsequently
annealed (at 1000 K) using ab-initio molecular dynamics (AIMD). This removes
coordination defects present in the MC models. The equilibrated structure at
this temperature was then force-relaxed using conjugate-gradient (CG)
optimization. This hybrid approach (MC + AIMD + 0K DFT-CG optimization)
produced good atomistic models of IPG which can reproduce experimentally
observed electronic band-gap, vibrational density of states (VDOS), magnetic
moment of Fe, the elastic constants as well as optical and dielectric
properties. Computationally expensive melt-quench simulation can be avoided
using present approach allowing the use of DFT for accurate calculations of
properties of complex glass like IPG.
