期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2019
卷号：116
期号：39
页码：19324-19329
DOI：10.1073/pnas.1909446116
出版社：The National Academy of Sciences of the United States of America
摘要：Neighborite, NaMgF 3, is used as a model system for understanding phase transitions in ABX 3 systems (e.g., MgSiO 3 ) at high pressures. Here we report diamond anvil cell experiments that identify the following phases in NaMgF 3 with compression to 162 GPa: NaMgF 3 (perovskite) → NaMgF 3 (post-perovskite) → NaMgF 3 (Sb 2 S 3 -type) → NaF (B2-type) + NaMg 2 F 5 ( P2 1 /c ) → NaF (B2) + MgF 2 (cotunnite-type). Our results demonstrate the existence of an Sb 2 S 3 -type post-post-perovskite ABX 3 phase. We also experimentally demonstrate the formation of the P2 1 /c AB 2 X 5 phase which has been proposed theoretically to be a common high-pressure phase in ABX 3 systems. Our study provides an experimental observation of the full sequence of phase transitions from perovskite to post-perovskite to post-post-perovskite followed by 2-stage breakdown to binary compounds. Notably, a similar sequence of transitions is predicted to occur in MgSiO 3 at ultrahigh pressures, where it has implications for the mineralogy and dynamics in the deep interior of large, rocky extrasolar planets..
