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

Abstract

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 ͕101͖ and ͕100͖ faces has been determined. We found that the ͕101͖ faces are terminated by a layer of K 1 ions and not by H 2 PO 2 4 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. [S0031-9007(98)

Remarkable enhancement in crystalline perfection, second harmonic generation efficiency, optical transparency, and laser damage threshold in potassium dihydrogen phosphate crystals by L-threonine doping

“…The added impurity ions block the prismatic ͑100͒ faces and therefore lead to faster growth rate for ͑101͒ pyramidal planes. 9 To reveal the influence of LT doping on the structure of KDP crystals the powdered specimens of pure and doped crystals were subjected to a PW1830 Philips analytical x-ray diffractometer with nickel filtered Cu K ␣ radiation ͑35 kV, 30mA͒. The powders of the homogeneous particle size were obtained by crushing and filtering by the sieve of ϳ25 micron aperture opening.…”

“…The impurity molecules and cations get easily adsorbed on the neutral ͑100͒ surfaces as compared to that of the ͑101͒ planes with positive charge due to termination of the surfaces with K + and lead to faster growth of these planes. 9 Adsorbed dopant molecules on ͑100͒ surface also create the hindrance for the impurity molecules to enter into the crystalline matrix and lead to better crystalline perfection. However, the possibility of some portion of the LT dopants at substitutional sites cannot be ruled out.…”

“…4,5 In parallel to the invention of new NLO materials, it is also important to modify the physical, optical, and electrical properties of these materials either by adding functional groups 6 or incorporation of dopants 7,8 for tailor made applications. In the presence of dopants growth promoting factors like growth rate 9 and many of the useful physical properties like optical transparency, 10,11 second harmonic generation ͑SHG͒ efficiency, 8 laser damage threshold ͑LDT͒, etc., get enhance. The dopants or additives also influence the crystalline perfection which may in turn influence the physical properties depending on the degree of doping and as per the accommodating capability of the host crystal.…”

Structure of Barite (001)− and (210)−Water Interfaces

“…To date, relatively few mineral-water interfaces have been characterized by highresolution structural measurements. [12][13][14][15][16][17] Other comparable studies have been of electrode-electrolyte interfaces under potentiometric control. [18][19][20] Thus we can begin to compare trends in the near-surface water structures among these different systems.…”

Liquid ordering at the Brushite-{010}–water interface

“…Furthermore, the knowledge of the surface structure is needed to explain the influence of the impurities on the growth morphology. 24,25 In biological mineralization, organic macromolecules are utilized to control the size, shape, and orientation of the crystals, the same properties that are of importance for creating good ceramic materials for production of artificial implants and other medical devices. We hope that our results on the most prominent crystal face of brushite will help to develope the controlled growth of this important biomineral.…”