The Influence of Alcohols in Driving the Morphology of Magnesium Chloride Nanocrystals

MgCl2 nanocrystals prepared in the presence of methanol and ethanol were characterized by complementing surface-science tools with a systematic quantum-mechanical investigation of the stability order (in terms of Gibbs free energy) of different MgCl2 surfaces in the presence of the two alcohols. Both alcohols drastically change the overall stability and the stability order of the exposed surfaces, mainly as a consequence of the entropic contribution to the Gibbs free energy, hence inhibiting or promoting crystal growth in certain directions. The environment-dependent occurrence of the MgCl2 surfaces may influence the structure and properties of the supported TixCl4@x sites in the MgCl2/TiCl4 precatalyst, which has important implications in the design of morphologically controlled Ziegler-Natta catalysts.