Authors: Raphael Shirley, Yaoyao Liu, Tim Totton, Richard H. West, and Markus Kraft*

AlCl₃ is added in small quantities to TiCl₄ fed to industrial reactors during the combustion synthesis of titanium dioxide nanoparticles in order to promote the rutile crystal phase. Despite the importance of this process a detailed mechanism including AlCl₃ is still not available. This work presents the thermochemistry of many of the intermediates in the early stages of the mechanism, computed using quantum chemistry. The enthalpies of formation and thermochemical data for AlCl, AlO, AlOCl, AlOCl₂, AlO₂, AlO₂Cl, AlOCl₃, AlO₂Cl₂, AlO₃ClTi, AlO₂Cl₂Ti, AlO₂Cl₄Ti, AlOCl₅Ti, AlO₂Cl₃Tia, AlO₂Cl₂Ti, AlO₂Cl₅Ti, AlOCl₄Ti, AlO₂Cl₃Tib, AlCl7Ti, AlCl₆Ti, Al₂Cl₆, Al₂O₂Cl, Al₂O₂Cl₃, Al₂O₃Cl₂, Al₂O₂Cl₂, Al₂OCl₄, Al₂O₃, and Al₂OCl₃ were calculated using density functional theory (DFT). A full comparison between a number of ab initio methods is made for one of the important species, AlOCl, in order to validate the use of DFT and gauge the magnitude of errors involved with this method. Finally, equilibrium calculations are performed to try to identify which intermediates are likely to be most prevalent in the high temperature industrial process, and as a first attempt to characterize the nucleation process.

• This paper draws from preprint 74: First-principles thermochemistry for the combustion of a TiCl₄ and AlCl₃ mix.

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