Atomistic simulation of oxide surfaces and their reactivity with water

Atomistic simulation is a valuable tool for interpreting and predicting sur face structures. This paper describes our current work aimed at applying th is approach to model oxide surfaces in contact with water. The atomistic si mulation techniques used are energy minimisation and molecular dynamics, wh ich are coupled with interatomic potentials. Energy minimisation allows us to evaluate the most stable surface configurations and molecular dynamics p rovides the effect of temperature on the surface. The use of interatomic po tentials, which describe the forces between the atoms, allows the surface p roperties to be calculated rapidly hence enabling us to increase the comple xity of the systems studied. We have extended our previous work in two ways , first by modelling the interaction of water with more complex materials s uch as magnesium silicate and iron oxide and secondly, by considering the i nitial stages of dissolution by evaluating the energies of replacing the su rface cations with protons. We find that there is a strong interaction betw een the surfaces and water. The bonding of the surface to the water molecul es is dominated by the cation-water interactions but is moderated by the ar ea occupied by each water molecule, which is approximately 10 Angstrom(2). In addition, as expected, the dissolution energies are highly dependent on cation coordination and the type of cation present, with Ca being energetic ally more favoured than Mg, and the surface structure as illustrated by Fe2 O3.