  Magnetite has attracted increasing attention in recent years due to its
promising and diverse applications in biomedicine. Theoretical modelling can
play an important role in understanding magnetite-based nanomaterials at the
atomic scale for a deeper insight into the experimental observations. However,
calculations based on density functional theory (DFT) are too costly for
realistically large models of magnetite nanoparticles. Classical force field
methods are very fast but lack of precision and of the description of
electronic effects. Therefore, a cheap and efficient quantum mechanical
simulation method with comparable accuracy than DFT is highly desired. Here, a
less computational demanding DFT-based method, i.e. self-consistent charge
density functional tight-binding (SCC-DFTB), is adopted to investigate
magnetite bulk and low-index (001) surface with newly proposed parameters for
Fe-O interactions. We report that SCC-DFTB with on-site Coulomb correction
provides results in quantitatively comparable agreement with those obtained by
DFT+U and hybrid functional methods. Therefore, SCC-DFTB is valued as an
efficient and reliable method for the description magnetite. This assessment
will promote SCC-DFTB computational studies on magnetite-based nanostructures
that attract increasing attention for medical applications.
