First-principles thermochemistry for the combustion of a TiCl4 and AlCl3 mixture.

AlCl(3) is added in small quantities to TiCl(4) 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 AlCl(3) 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, AlOCl(2), AlO(2), AlO(2)Cl, AlOCl(3), AlO(2)Cl(2), AlO(3)ClTi, AlO(2)Cl(2)Ti, AlO(2)Cl(4)Ti, AlOCl(5)Ti, AlO(2)Cl(3)Tia (isomer-a), AlO(3)Cl(2)Ti, AlO(2)Cl(5)Ti, AlOCl(4)Ti, AlO(2)Cl(3)Tib (isomer-b), AlCl(7)Ti, AlCl(6)Ti, Al(2)Cl(6), Al(2)O(2)Cl, Al(2)O(2)Cl(3), Al(2)O(3)Cl(2), Al(2)O(2)Cl(2), Al(2)OCl(4), Al(2)O(3), and Al(2)OCl(3) were calculated using density functional theory (DFT). A full comparison between a number of methods is made for one of the important species, AlOCl, 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.