title: Metastable Layered Cobalt Chalcogenides from Topochemical Deintercalation.
abstract: We present a general strategy to synthesize metastable layered materials via topochemical deintercalation of thermodynamically stable phases. Through kinetic control of the deintercalation reaction, we have prepared two hypothesized metastable compounds, CoSe and CoS, with the anti-PbO type structure from the starting compounds KCo2Se2and KCo2S2, respectively. Thermal stability, crystal structure from X-ray and neutron diffraction, magnetic susceptibility, magnetization, and electrical resistivity are studied for these new layered chalcogenides; both CoSe and CoS are found to be weak itinerant ferromagnets with Curie temperatures close to 10 K. Due to the weak van der Waals forces between the layers, CoSe is found to be a suitable host for further intercalation of guest species such as Li-ethylenediamine. From first-principles calculations, we explain why the Co chalcogenides are ferromagnets instead of superconductors as in their iron analogues. Bonding analysis of the calculated electronic density of states both explains their phase stability and predicts the limits of our deintercalation technique. Our results have broad implications for the rational design of new two-dimensional building blocks for functional materials.
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Xiuquan
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland , College Park, Maryland 20742, United States.|Center for Nanophysics and Advanced Materials, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Brandon
authors.initials: B
authors.lastname: Wilfong
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Hector
authors.initials: H
authors.lastname: Vivanco
authors.affiliation: Center for Nanophysics and Advanced Materials, University of Maryland , College Park, Maryland 20742, United States.|Department of Physics, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Johnpierre
authors.initials: J
authors.lastname: Paglione
authors.affiliation: Center for Neutron Research, National Institute of Standards and Technology , Gaithersburg, Maryland 20899, United States.
authors.forename: Craig M
authors.initials: CM
authors.lastname: Brown
authors.affiliation: Department of Chemistry and Biochemistry, University of Maryland , College Park, Maryland 20742, United States.|Center for Nanophysics and Advanced Materials, University of Maryland , College Park, Maryland 20742, United States.
authors.forename: Efrain E
authors.initials: EE
authors.lastname: Rodriguez