A molecular dynamics study on the interfacial properties of millerite

Abstract

The present study aims at developing force field parameters for describing the millerite structure and subsequently for investigation of its interfacial properties under varying conditions within the framework of molecular dynamics simulations. The first set of calculations were performed to obtain the required force field parameters, validated through reproduction of the bulk properties. This was followed by estimation of the surface energy and evaluation of the collector physisorption onto the non-polar (100) and (110) surfaces. Collector molecules exhibited higher affinity towards the former, with the branched alkyl chain favoring the interactions with either of the surfaces. Further simulations were conducted to examine the changes in the contact angle of the intrinsically hydrophilic (110) surface upon oxidization. Observations through transition from the neutral surface fully covered by elemental sulfur to a charge-bearing surface containing sulfur and polysulfides were compared against the theoretical predictions made by the Lippmann equation, and the discrepancies were attributed to the significance of line tension at the atomic scale. Finally, propensity of collector molecules towards the positively and negatively charged (110) surface was examined in the absence and presence of excess calcium hydroxide. In both cases, the collector-surface interactions were impeded in the strong alkaline solution.