High-Pressure, High-Temperature Single-Crystal Growth, Ab initio Electronic Structure Calculations, and Equation of State of ε-Fe3N1+x
datasetposted on 27.01.2009 by Rainer Niewa, Dieter Rau, Aron Wosylus, Katrin Meier, Michael Hanfland, Michael Wessel, Richard Dronskowski, Dmytro A. Dzivenko, Ralf Riedel, Ulrich Schwarz
Datasets usually provide raw data for analysis. This raw data often comes in spreadsheet form, but can be any collection of data, on which analysis can be performed.
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.