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- Title
Novel High-Temperature Modification of Belomarinaite KNaSO 4 : Crystal Structure and Thermal Order–Disorder Phase Transitions.
- Authors
Shablinskii, Andrey; Bubnova, Rimma; Shorets, Olga; Krzhizhanovskaya, Maria; Volkov, Sergey; Filatov, Stanislav
- Abstract
Belomarinaite KNaSO4 (space group P3m1, a = 5.6072(3), c = 7.1781(4) Å and Z = 2) has been studied by high-temperature single crystal X-ray diffraction. The K and Na atoms are disordered, and M1(1c) and M2(1b) sites merge into an M1(2d)(K50%/Na50%) site with increasing temperature, and novel translationsgleiche phase transition of belomarinaite KNaSO4 (P3m1 → P-3m1) was revealed at 123 °C. Then, the temperature increase leads to phase transition of P 3 ¯ m 1 -polymorph of KNaSO4 to α-KNaSO4 (P63/mmc) at 446 °C, and sodium and potassium atoms in K1(1a) and Na1(1b) sites merged into an M4(2a)(K50%/Na50%) site. Crystal structures of KNaSO4 were refined at 300, 500 and 750 °C to R1 = 0.057, 0.056 and 0.048, respectively. The BVS maps and bond-valence energy landscape (BVEL) have been calculated, and the probability of the Na+ migration has been predicted using structural data for belomarinaite at 25 °C. The Na+ ion migration can occur at 2.14 eV in the ab plane and 2.80 eV along the c axis at 25 °C.
- Subjects
ORDER-disorder transitions; CRYSTAL structure; PHASE transitions; SPACE groups; ION migration &; velocity
- Publication
Crystals (2073-4352), 2024, Vol 14, Issue 1, p27
- ISSN
2073-4352
- Publication type
Article
- DOI
10.3390/cryst14010027