Surface structure refinement including anomalous crystal truncation rods

A surface structure refinement procedure is introduced, which uses both anomalous and non-anomalous crystal truncation rod data simultaneously. It is shown how a single structural model can be refined against data sets measured at different wavelengths and how this can greatly reduce correlations between fit parameters. The structure factors are computed taking into account the anomalous dispersion corrections and are scaled to the data, whereby each data set is assigned its own scale factor. The procedure is implemented in the widely used surface diffraction program ROD. The structure of a one unit cell thin LaAlO₃ film on an SrTiO₃(001) substrate is refined by making use of a non-anomalous data set and one taken at the La L₁-edge.