Quantenchemische Untersuchungen an Nitriden der Platingruppenmetalle

This work presents a comprehensive theoretical investigation of the binary and ternary nitrides of the platinum group metals. It is based on density-functional theory using different methods. The binary and unknown mono-nitrides of ruthenium, rhodium, palladium, osmium, and iridium proved to be thermodynamically unstable at standard pressure, but become stable at high pressures. Calculating the enthalpy of formation against pressure resulted in the required synthesis pressure. This is 9 GPa for RuN in the zinc blende type, 22 GPa for OsN in the wurtzite type and 25/22 GPa for RhN/IrN in the cooperite type. For PdN the needed pressure is beyond 60 GPa. This data only holds for 0 Kelvin, at usual synthesis temperatures the pressures will be higher due to the large entropy of gaseous nitrogen. A thermodynamical approximation allowed for this temperature-pressure dependency explicitly. One section is dedicated to the 2004 published PtN. The existence of this nitride in the zinc blende structure has been falsified in this work, the cooperite type as being the most promising candidate for a platinum mono-nitride has been figured out. Later, the synthesized compound has been identified to be a platinum pernitride with pyrite structure. Another section deals with Pd2N. This characterized compound (Co2N type) expanded its volume in the calculation of about 30 percent, full relaxation yielded a more stable tetragonally distorted cuprite type-Pd2N. The structure with the published values would sense an internal pressure of 89 GPa and is 270 kJ/mol more unstable with respect to the cuprite structure. Therefore, the existence of Pd2N is impossible from the theoretical point of view. The structure should be reviewed and, if necessary, removed from the International Crystal Structure Database (ICSD). Within the ternary phases the ferromagnetic nitrides of type MFe3N in the perovskite-like type and of type M2Mo3N in the filled beta-manganese type have been investigated. For both structure types the compounds with M = Pd, Pt are known. Its physical properties have been excellently reproduced by the calculations. For the unknown IrFe3N a transition pressure of 37 GPa has been calculated. RhFe3N has been figured out to be stable even at standard pressure. The compound is predicted to have a remarkable saturation magnetization. Driven by these results, the compound has been synthesized a couple of months later. All properties are in excellent harmony with the theoretical results in this work.

Grantor dc:publisher

Shaker

Year dc:date

2006

Author dc:creator

• von Appen, Jörg

Contributors dc:contributor

• Dronskowski, Richard

• info:eu-repo/classification/ddc/540
• Chemie
• Nitride
• DFT
• Platinmetalle
• Quantenchemie
• nitrides
• density functional theory
• platinum group
• quantum chemistry

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-121425%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:59661