Functionalized Amorphous Carbon Materials via Reactive Molecular Dynamics Simulations

We derive a database of atomistic structural models of
amorphous
carbon materials endowed with exohedral functional groups. We start
from phases previously derived using the DynReaxMas method for reactive
molecular dynamics simulations, which exhibit atomistic and medium-length-scale
features in excellent agreement with available experimental data.
Given a generic input structure/phase, we develop postprocessing simulation
algorithms mimicking experimental preparation protocols aimed at:
(1) “curing” the phase to decrease the defect concentration;
(2) automatically selecting the most reactive carbon atoms via interaction
with a probe molecular species, and (3) stabilizing the phase by saturating
the valence of carbon atoms with single-bond functional groups. Although
we focus on oxygen-bearing functionalities, they can be replaced with
other monovalent groups, such as –H, –COOH, –CHO,
so that the protocol is quite general. We finally classify reactive
sites in terms of their location within the structural framework and
coordination environment (edges, tunnels, rings, aromatic carbons
becoming aliphatic) and try to single out descriptors that correlate
with tendency to functionalization.