A new high-pressure CaGe2O5 polymorph with 5- and 6-coordinated germanium

Péter Németh; Kurt Leinenweber; Thomas L. Groy; Peter R. Buseck

doi:10.2138/am.2007.2411

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Letter| February 01, 2007

A new high-pressure CaGe2O5 polymorph with 5- and 6-coordinated germanium

Péter Németh;

Péter Németh

1

School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, U.S.A.

2

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

*

Present address: Chemical Research Center of the Hungarian Academy of Sciences, Budapest, Pusztaszeri út 59-67, 1025, Hungary. E-mail: peter.nemeth@chemres.hu

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Kurt Leinenweber;

Kurt Leinenweber

2

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

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Thomas L. Groy;

Thomas L. Groy

2

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

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Peter R. Buseck

1

School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, U.S.A.

2

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

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Author and Article Information

Péter Németh

*

Present address: Chemical Research Center of the Hungarian Academy of Sciences, Budapest, Pusztaszeri út 59-67, 1025, Hungary. E-mail: peter.nemeth@chemres.hu

1

School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, U.S.A.

2

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

Kurt Leinenweber

2

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

Thomas L. Groy

2

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

Peter R. Buseck

1

School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287-1404, U.S.A.

2

Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604, U.S.A.

Publisher: Mineralogical Society of America

Received: 08 Aug 2006

Accepted: 25 Sep 2006

First Online: 09 Mar 2017

Online ISSN: 1945-3027

Print ISSN: 0003-004X

American Mineralogist (2007) 92 (2-3): 441–443.

https://doi.org/10.2138/am.2007.2411

Abstract

We discovered a new CaGe₂O₅ polymorph in high-pressure experiments (above 8 GPa). The phase is orthorhombic, space group Pbam, with a = 7.306(2), b = 8.268(2), c = 5.714(1) Å, V = 345.2(1) Å³, and Z = 4. The new phase, which we call post-titanite CaGe₂O₅, is the high-pressure polymorph of titanite CaGe₂O₅. The structure of this new polymorph is based on a network of 5- and 6-coordinated Ge polyhedra and 8-coordinated Ca atoms. Following the germanate analog to silicate, post-titanite CaSi₂O₅ could be expected to form at high-pressure conditions and thus might exist in Earth’s mantle.