High-Pressure Phase Transition in Cs2KMnF6

✍ Scribed by Y. Xu; K. Söderberg; R. Norrestam

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 231 KB
• Volume: 153
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8748

✦ Synopsis

The stability of the cubic high-temperature (HT) form of Cs 2 KMnF 6 , with an elpasolite structure, is studied at elevated pressures. The present study shows that the HT form of Cs 2 KMnF 6 undergoes a pressure-induced phase transition at 40 kbar to a more ordered high-pressure (HP) phase of lower symmetry. The space group symmetry of the HP phase, I4/mmm, is the same as that observed for the low-temperature (LT) phase. High-pressure studies performed on the LT phase indicated no transitions up to 50 kbar and gave compressibility features similar to those obtained for the HP phase. Singlecrystal X-ray di4raction data for the HP phase were collected at 44 kbar. Re5ning nine structural parameters against 69 independent signi5cant re6ections gave a linear R value of 0.072 (wR ‫؍‬ 0.086). The values of the positional parameters are in agreement with those observed for the LT phase under ambient conditions. The transition characteristics for the HT form depend on the crystal quality and/or the pressure transmitting media used. With liquid argon, loaded into the pressure cell at low temperature and ambient pressure, the transition pressure became 30 kbar. With methanol:ethanol:water, loaded under ambient conditions, the transition was observed at 40 kbar.