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.