With this study on KDP, we present an interface atomic structure determination of a crystal in contact with its growth solution. Using x-ray diffraction at a third-generation synchrotron radiation source, the structure of both the {101} and {100} faces has been determined. We found that the {101} faces are terminated by a layer of K+ ions and not by H2PO4- groups, resolving a long-standing issue that could not be predicted by theory. This result leads to an atomic-scale explanation of the influence of metal impurities on the macroscopic growth morphology.

Phys. Rev. Lett.

de Vries, S.A, Goedtkindt, P, Bennett, S.L, Huisman, W.J, Zwanenburg, M.J, Smilgies, D.-M, … Vlieg, E. (1998). Surface atomic structure of KDP crystals in aqueous solution: An explanation of the growth shape. Phys.Rev.Lett., 80, 2229–2232.