Mechanistic Insights into the Reaction between Mg and TiCl₄ from First-Principles Molecular Dynamics Simulations

The reaction mechanism between magnesium (Mg) and titanium tetrachloride (TiCl₄) is crucial for producing a titanium sponge. Experimental investigation is challenging due to high temperatures and chlorine's corrosiveness. The study used density functional theory combined with first-principles molecular dynamics (FPMD) at 1123 K to 1373 K to analyze the reaction mechanism. Initially, TiCl₄ is directly reduced by Mg in a stepwise manner: TiCl₄ → TiCl₃ → TiCl₂ → TiCl → Ti atoms. The intermediate TiCl_n species (n = 1-3) formed undergo reverse reactions and aggregate into Cl-bridged multinuclear low-valence titanium chlorides. These Cl-bridged species transform into Ti-bonded multinuclear low-valence titanium chlorides supported by MgCl₂. After forming Ti-bonded multinuclear species, the reduction proceeds via an electrochemically mediated reduction (EMR) pathway. In the EMR step, electrons transfer from Mg to chlorine, then from chlorine to titanium. Enhancing the electrochemical reduction step could significantly improve the overall reaction rate of Mg reducing TiCl₄.