Structure and Stability of Hydrolysis Reaction Products of MgO Nanoparticles Leading to the Formation of Brucite

Abstract

The bottom-up formation of MgxOy(OH)z nanoparticles leading to Mg(OH)2 nanoparticles was modeled in two steps by using an evolutionary global optimization approach: (1) the formation of small MgnOm+nH2m clusters via the hydrolysis of (MgO)n and (2) the formation of multilayered (Mg(OH)2)n clusters via monolayer stacking. The sheet-like (Mg(OH)2)n structures were predicted as the energetically favorable reaction products for the (MgO)n + nH2O reaction, whereas more compact structures were found to dominate for the products of (MgO)n + mH2O, m < n. The stepwise hydrolysis reactions most likely follow the compact reaction path until the crossover point is reached. Multistep structural rearrangements are required for the conversion between the compact products and the sheet-like products even after the crossover point. The protective shell formed by the hydroxyl groups may inhibit the further hydrolysis reaction of the compact products, even though the hydrolysis reactions are both exothermic and exergonic; s...