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High-Pressure, High-Temperature Single-Crystal Growth, Ab initio Electronic Structure Calculations, and Equation of State of ε-Fe3N1+x

Niewa, Rainer and Rau, Dieter and Wosylus, Aron and Meier, Katrin and Hanfland, Michael and Wessel, Michael and Dronskowski, Richard and Dzivenko, Dmytro A. and Riedel, Ralf and Schwarz, Ulrich (2009):
High-Pressure, High-Temperature Single-Crystal Growth, Ab initio Electronic Structure Calculations, and Equation of State of ε-Fe3N1+x.
In: Chemistry of Materials, ACS, pp. 392-398, 21, (2), ISSN 0897-4756,
[Online-Edition: http://dx.doi.org/10.1021/cm802721k],
[Article]

Abstract

The high-pressure behavior of the hard material ε-Fe3N1+x was studied up to 33 GPa with in situ X-ray diffraction experiments using diamond anvil cells in combination with synchrotron radiation as well as by ex situ high-temperature, high-pressure treatment at 1600(200) K in a two-stage multianvil device with a Walker-type module. Evaluation of the pressure−volume data up to 10 GPa by fitting a Murnaghan-type equation reveals a bulk modulus of B0 = 172(4) GPa (B′ = 5.7, fixed). The calculated bulk modulus (220 GPa) on the basis of density-functional theory (GGA-PAW-PBE) is in satisfying agreement with the experimental one. Single crystals of ε-Fe3N1+x as obtained by ex situ high-temperature, high-pressure experiments reveal in X-ray diffraction data refinements a structural model of iron atoms in the motif of a hexagonal close packing with occupation of octahedral voids by nitrogen atoms exhibiting long-range order. The preferred structural model is described in space group P312 (a = 4.7241(2) Å, c = 4.3862(2) Å, V = 84.773(6) Å3, Z = 2, R(F) = 0.0339, wR(F2) = 0.0556) and compared to a second model in P6322. This choice of structural description is corroborated by the results of density-functional calculations. These yield a total energy at 0 K, which is 5 kJ/mol lower for the model in space group P312 compared to the second best alternative arrangement. Using micro- and nanoindentation techniques, a Vickers hardness of HV = 7.4(10) GPa, a nanoindentation hardness of H = 10.1(8) GPa, as well as a reduced elastic modulus in the amount of Er = 178(11) GPa were measured for ε-Fe3N1+x single crystals.

Item Type: Article
Erschienen: 2009
Creators: Niewa, Rainer and Rau, Dieter and Wosylus, Aron and Meier, Katrin and Hanfland, Michael and Wessel, Michael and Dronskowski, Richard and Dzivenko, Dmytro A. and Riedel, Ralf and Schwarz, Ulrich
Title: High-Pressure, High-Temperature Single-Crystal Growth, Ab initio Electronic Structure Calculations, and Equation of State of ε-Fe3N1+x
Language: English
Abstract:

The high-pressure behavior of the hard material ε-Fe3N1+x was studied up to 33 GPa with in situ X-ray diffraction experiments using diamond anvil cells in combination with synchrotron radiation as well as by ex situ high-temperature, high-pressure treatment at 1600(200) K in a two-stage multianvil device with a Walker-type module. Evaluation of the pressure−volume data up to 10 GPa by fitting a Murnaghan-type equation reveals a bulk modulus of B0 = 172(4) GPa (B′ = 5.7, fixed). The calculated bulk modulus (220 GPa) on the basis of density-functional theory (GGA-PAW-PBE) is in satisfying agreement with the experimental one. Single crystals of ε-Fe3N1+x as obtained by ex situ high-temperature, high-pressure experiments reveal in X-ray diffraction data refinements a structural model of iron atoms in the motif of a hexagonal close packing with occupation of octahedral voids by nitrogen atoms exhibiting long-range order. The preferred structural model is described in space group P312 (a = 4.7241(2) Å, c = 4.3862(2) Å, V = 84.773(6) Å3, Z = 2, R(F) = 0.0339, wR(F2) = 0.0556) and compared to a second model in P6322. This choice of structural description is corroborated by the results of density-functional calculations. These yield a total energy at 0 K, which is 5 kJ/mol lower for the model in space group P312 compared to the second best alternative arrangement. Using micro- and nanoindentation techniques, a Vickers hardness of HV = 7.4(10) GPa, a nanoindentation hardness of H = 10.1(8) GPa, as well as a reduced elastic modulus in the amount of Er = 178(11) GPa were measured for ε-Fe3N1+x single crystals.

Journal or Publication Title: Chemistry of Materials
Volume: 21
Number: 2
Publisher: ACS
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Dispersive Solids
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 12 Apr 2012 08:27
Official URL: http://dx.doi.org/10.1021/cm802721k
Identification Number: doi:10.1021/cm802721k
Funders: This work was supported by the Elitenetzwerk Bayern within the Advanced Materials Science program, This work was supported by the Max-Planck-Gesellschaft, This work was supported within the priority program “Synthesis, in situ characterisation and quantum mechanical modelling of Earth Materials, oxides, carbides and nitrides at extremely high pressures and temperatures” of the D FG (SPP 1236)
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