Deconstructing the Structural Convergence of the (110) Surface of Rutile TiO₂

In response to a recent high-precision LEED-IV experiment, we have carried out a detailed reexamination of the (110) surface structure of rutile TiO₂ using first-principles total-energy methods. Our previous analysis showed that bond lengths between surface atoms converge much faster with respect to model approximations than do relaxed absolute atomic positions. This difference in convergence rate is due to the relatively slow convergence of bond angles. We argue that this analysis favors altering the way structural data are typically reported for covalently bonded solids from absolute atomic positions to more physically meaningful quantities such as bond lengths and angles.