Temperature Behavior of Precursor Clusters at the Pre-Crystallization Phase of K(H<sub>2</sub>PO<sub>4</sub>) Studied by SAXS
Andrey E. Sukhanov,
Kseniia B. Ilina,
Petr V. Konarev,
Georgy S. Peters,
Yury V. Pisarevsky,
Ekaterina S. Smirnova,
Olga A. Alekseeva,
Mikhail V. Kovalchuk
Affiliations
Andrey E. Sukhanov
A.V. Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, 59, Leninskii Prospect, Moscow 119333, Russia
Kseniia B. Ilina
A.V. Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, 59, Leninskii Prospect, Moscow 119333, Russia
Petr V. Konarev
A.V. Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, 59, Leninskii Prospect, Moscow 119333, Russia
Georgy S. Peters
National Research Centre “Kurchatov Institute”, 1, Akademika Kurchatova Pl., Moscow 123182, Russia
Yury V. Pisarevsky
A.V. Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, 59, Leninskii Prospect, Moscow 119333, Russia
Ekaterina S. Smirnova
A.V. Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, 59, Leninskii Prospect, Moscow 119333, Russia
Olga A. Alekseeva
A.V. Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, 59, Leninskii Prospect, Moscow 119333, Russia
Mikhail V. Kovalchuk
A.V. Shubnikov Institute of Crystallography, Federal Scientific Research Centre “Crystallography and Photonics”, Russian Academy of Sciences, 59, Leninskii Prospect, Moscow 119333, Russia
Elementary building blocks for the growth of KDP crystals were established. The solution of potassium dihydrogen phosphate (KH2PO4–KDP) has been experimentally studied by the small-angle X-ray scattering (SAXS) method. The analysis of SAXS data in the temperature range of 2.5–90 °C using a set of models of 3D fragments of the crystal structure showed that the saturated solution contains above K+, H2PO4− and KH2PO4 monomers, as well as mainly octamers. The 3D model of the octamer isolated from the crystal structure has dimensions of 17.443 Å along the [001] axis and 5.963 Å along the [100] and [010] axes. As the temperature is decreased, starting from the saturation temperature of the solution, the volume fraction of octamers sharply increases while the volume fraction of monomers decreases. The results indicate that the monomers and octamers represent major components in the solution with the presence of minor populations of other oligomers. The significant dominance of octamers in the supersaturated solution indicates that they are elementary building blocks for the growth of KDP crystals of tetragonal modification.
