Surface Atomic Structure of KDP Crystals in Aqueous Solution: An Explanation of the Growth Shape

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 H₂PO₄^0ex0ex- 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.