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Main Authors: Mustafa, Luqman, Kunzmann, Susanne, Kostka, Martin, Fortmann, Jill, Mockute, Aurelija, Savan, Alan, Ludwig, Alfred, Grünebohm, Anna, Kreyssig, Andreas, Böhmer, Anna E.
Format: Preprint
Published: 2026
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Online Access:https://arxiv.org/abs/2601.21790
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author Mustafa, Luqman
Kunzmann, Susanne
Kostka, Martin
Fortmann, Jill
Mockute, Aurelija
Savan, Alan
Ludwig, Alfred
Grünebohm, Anna
Kreyssig, Andreas
Böhmer, Anna E.
author_facet Mustafa, Luqman
Kunzmann, Susanne
Kostka, Martin
Fortmann, Jill
Mockute, Aurelija
Savan, Alan
Ludwig, Alfred
Grünebohm, Anna
Kreyssig, Andreas
Böhmer, Anna E.
contents Transition-metal dichalcogenides of the pyrite-marcasite family are model systems of crystal chemistry. A few of these show polymorphism. The theoretical ground state of CoSe2 is marcasite, but the material is typically synthesized in the pyrite structure. Polymorphism has been observed in nanoparticles and synthetic control of the polymorphs of CoSe2 has not been achieved. We have synthesized material libraries of the Fe1-xCoxSe2 series by combining combinatorial deposition and ex-situ selenization. The approach allows to efficiently explore substitution ranges and crystal structures that form for different synthesis conditions. We find that higher levels of Co content x within the marcasite structure are possible when synthesizing at low temperatures. At a synthesis temperature of only 250° C, we have successfully synthesized marcasite CoSe2 as the majority phase. Density functional theory simulations reveal that the two isomorphs of CoSe2 are extremely close in energy and that the orthorhombic phase is the energetic ground state. Our experimental and theoretical data show that the marcasite structure is the equilibrium phase of Fe1-xCoxSe2 in the entire composition range.
format Preprint
id arxiv_https___arxiv_org_abs_2601_21790
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Synthetic control over marcasite-pyrite polymorph formation in the Fe1-xCoxSe2 series
Mustafa, Luqman
Kunzmann, Susanne
Kostka, Martin
Fortmann, Jill
Mockute, Aurelija
Savan, Alan
Ludwig, Alfred
Grünebohm, Anna
Kreyssig, Andreas
Böhmer, Anna E.
Materials Science
Transition-metal dichalcogenides of the pyrite-marcasite family are model systems of crystal chemistry. A few of these show polymorphism. The theoretical ground state of CoSe2 is marcasite, but the material is typically synthesized in the pyrite structure. Polymorphism has been observed in nanoparticles and synthetic control of the polymorphs of CoSe2 has not been achieved. We have synthesized material libraries of the Fe1-xCoxSe2 series by combining combinatorial deposition and ex-situ selenization. The approach allows to efficiently explore substitution ranges and crystal structures that form for different synthesis conditions. We find that higher levels of Co content x within the marcasite structure are possible when synthesizing at low temperatures. At a synthesis temperature of only 250° C, we have successfully synthesized marcasite CoSe2 as the majority phase. Density functional theory simulations reveal that the two isomorphs of CoSe2 are extremely close in energy and that the orthorhombic phase is the energetic ground state. Our experimental and theoretical data show that the marcasite structure is the equilibrium phase of Fe1-xCoxSe2 in the entire composition range.
title Synthetic control over marcasite-pyrite polymorph formation in the Fe1-xCoxSe2 series
topic Materials Science
url https://arxiv.org/abs/2601.21790