Study of Ammonia Adsorption on Magnetite Surfaces with Molecular Dynamics Simulations

The present study proposes an atomistic molecular dynamics model system of a magnetite (Fe₃O₄) {111} surface. The effect of temperature on the adsorption process of ammonia (NH₃) at low concentrations in the aqueous phase has been considered. The molecular dynamics simulations were carried out using the Clay force field (Clay FF) with a modification for the iron atoms in the NPT ensemble at a pressure of 90 bar. The considered system was heated in a temperature range from 293 to 473 K, and additional relaxations were performed at temperatures of interest. Within the scope of this study, the basic parameters of the magnetite surface were calculated and the distances between the ammonia molecules and the surface were determined. A general idea of the degree and rate of adsorption at specific temperatures was obtained. The calculation results were compared to the experimental data where possible and to other available simulations of adsorption processes on metal oxides.