The conversion of ethanol to ethylene, which is one of the most important feed stocks for the petrochemical industry, is of particular commercial interest. Two mechanisms, stepwise and concerted, of the ethanol dehydration to ethylene in the presence of water have been investigated by the ONIOM model (14T/120T) with B3LYP/6-31g(d,p):UFF method. In the stepwise mechanism, the coadsorbed water as...