Assessing density functionals for the prediction of thermochemistry of Ti-O-Cl species.

Titanium dioxide (TiO2) nanoparticles are widely used in contaminant remediation, photocatalysis and solar cell manufacturing. The low-cost production of TiO2 nanoparticles via the combustion of titanium tetrachloride (TiCl4) in oxygen is thus an important industrial process. To accurately model the flame synthesis of TiO2 nanoparticles, reliable thermodynamic data of Ti-O-Cl species are indispensable but often unavailable. We therefore carried out benchmark calculations, using the left-eigenstate completely renormalized singles, doubles and perturbative triples (CR-CC(2,3), aka CR-CCL) method with the cc-pVTZ basis set, to obtain the equilibrium structures and vibrational frequencies of selected Ti-O-Cl species; we then performed single-point CCSD(T)/aug-cc-pV LZ () calculations to extrapolate the CCSD(T)/CBS energies. After analyzing the experimental and calculated enthalpy of selected Ti-O-Cl species, the standard enthalpy of formation of the TiOCl2 molecule is determined to be 600.5kJ/mol at 298K. The standard enthalpy of all other Ti-O-Cl species are determined accordingly. Finally, we assessed the accuracy of 42 popular density functionals for the Ti-O-Cl species. Among these assessed functionals, the B98 functional, tightly followed by B97-1 and B3LYP, exhibits the best overall performance in the prediction of the thermochemistry of the Ti-O-Cl species. We conducted coupled-cluster benchmark calculations for the Ti-O-Cl species. The standard enthalpy and Gibbs energy of formation of 28 Ti-O-Cl species were determined at temperatures from 0 K to 3000 K. Among the 42 assessed density functionals, we recommend using B98, B97-1, and/or B3LYP functionals for the prediction of thermochemistry of the Ti-O-Cl system. [ABSTRACT FROM AUTHOR]