Nature Communications 4: Article number: 2618 (2013); Published: 21 October 2013; Updated: 3 July 2014.

During the final stages of manuscript preparation, the fast Fourier transform (FFT) filtered images in the insets of Fig. 5a,b were inadvertently switched and labelled with the wrong crystallographic indices. Our analysis and conclusions remain unchanged by this error. The correct version of Fig. 5 appears below.

Figure 5