Journal Article

PUBDB-2026-00872

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Compressed $MgCl_2$ Reveals Multiple Pathways to Cotunnite Structures

Yin, Y. (Corresponding author) ; Dubrovinsky, L.Extern*XFEL.EU* ; Aslandukov, A. ; Aslandukova, A. ; Akbar, F. I. ; Zhou, W. ; Laniel, D.Extern* ; Pakhomova, A.Extern* ; Fedotenko, T.Extern*DESY* ; Glazyrin, K.XFEL.EU*DESY* ; Garbarino, G. ; Fang, H. ; Abrikosov, I. A. ; Dubrovinskaia, N.

2026
American Chemical Society Washington, DC

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Please use a persistent id in citations: doi:10.1021/acs.inorgchem.5c05774

Abstract: The phase transition sequences of MeX$_2$ compounds (Me = metal or, more generally, an electropositive element), whose constituent atoms contribute 16 valence electrons per formula unit under high pressure, are of fundamental importance in materials science, high-pressure chemistry, and mineral physics. Here, we report the first observation of trigonal prismatic coordination in this class of materials, realized in magnesium dichloride MgCl$_2$. We synthesized anhydrous MgCl$_2$ by the direct reaction of elemental magnesium with carbon tetrachloride (CCl$_4$) in laser-heated diamond anvil cells from 7(2) to 83(3) GPa. Single-crystal X-ray diffraction identified the known ${hP3}$-MgCl$_2$ polymorph at 7(2) GPa, and two previously unknown high-pressure phases: an orthorhombic oP72-MgCl2 at 28(2) and 44(3) GPa, and a cotunnite-type oP12-MgCl2 at 64(3), 73(3), and 83(3) GPa. The ${oP72}$ phase features distorted MgCl$_6$ trigonal prisms, while the oP12 phase adopts MgCl8 bicapped trigonal prisms. This sequence of ${hP3}$ → ${oP72}$ → ${oP12}$ reveals a complex pressure-induced structural transition from layered to three-dimensional frameworks. Ab initio calculations agree well with the experimental structural data, support the stability range of the new polymorphs, provide the equation of states, and reveal their electronic properties. Our findings demonstrate several transformation pathways by which MeX$_2$ compounds evolve toward cotunnite-type structures under compression.

Note: waiting for fulltext - 26.05.26

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Contributing Institute(s):

1. FS DOOR-User (FS DOOR-User)
2. Experimentebetreuung PETRA III (FS-PET-D)

Research Program(s):

1. 631 - Matter – Dynamics, Mechanisms and Control (POF4-631) (POF4-631)
2. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)

Experiment(s):

1. PETRA Beamline P02.2 (PETRA III)

Appears in the scientific report 2026

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Database coverage:
; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Ebsco Academic Search ; Essential Science Indicators ; IF < 5 ; JCR ; Nationallizenz ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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