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Authors: Ikeda, Yuji
Lehmann, Tanja S.
Widenmeyer, Marc
Coduri, Mauro
Grabowski, Blazej
Niewa, Rainer
Title: Crystal structure and phase stability of Co2N: a combined first-principles and experimental study
Issue Date: 2021 Zeitschriftenartikel 10 Journal of alloys and compounds, 854 (2021), 156341
ISBN: 0925-8388
Abstract: The crystal structure and phase stability of Co2N are revisited based on experiments and first-principles calculations. Powder X-ray diffraction (PXRD) measurements and Rietveld refinements clearly confirm that the stable crystal structure of Co2N is an isotype of η-Fe2C and Co2C with the space group Pnnm rather than the closely related ζ-Fe2N with the space group Pbcn. The refined lattice parameters of Co2N in the Pnnm structure are a = 4.6108(1) Å, b = 4.3498(1) Å, c = 2.85592(7) Å, obtained from X-ray diffraction using synchrotron radiation. Furthermore, differential scanning calorimetry (DSC) with subsequent diffraction experiments reveal an endothermal transition to an ε-type order at 398 °C followed by an exothermal decomposition at 446 °C. First-principles density-functional-theory (DFT) calculations including the Hubbard U correction (DFT+U) demonstrate that it is essential for transition metal nitrides to consider strong electron correlation to predict the correct experimental structure and magnetic state. In particular, an effective value of Ueff = 2.75 eV can be utilized to obtain an antiferromagnetic Pnnm phase of Co2N in agreement with experiments.
Appears in Collections:03 Fakultät Chemie

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