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. 2017 Dec 13;3(12):e1701816. doi: 10.1126/sciadv.1701816

Fig. 1. SOAP-GAP predictions for silicon surfaces.

Fig. 1

(A) The tilt angle of dimers on the reconstructed Si(100) surface [left, STM image (13); right, SOAP-GAP–relaxed structure] is the result of a Jahn-Teller distortion, predicted to be about 19° by DFT and SOAP-GAP. Empirical force fields show no tilt. (B) The Si(111)–7 × 7 reconstruction is an iconic example of the complex structures that can emerge from the interplay of different quantum mechanical effects [left, STM image (14); right, SOAP-GAP–relaxed structure colored by predicted local energy error when using a training set without adatoms]. (C) Reproducing this delicate balance and predicting that the 7 × 7 is the ground-state structure is one of the historical successes of DFT: a SOAP-based ML model is the only one that can describe this ordering, whereas widely used force fields incorrectly predict the unreconstructed surface (dashed lines) to a lower-energy state.