Transition Metal Nitrides (TMN) are of considerable importance for the industry and have gathered a great deal of interest in the scientific community, mostly due to their unique physical and mechanical properties. To increase the understanding of what enables them to have such extraordinary properties requires the study of lattice dynamics and their phonon dispersion. In this thesis, the transition metal nitride, TaN, is studied extensively along with preliminary results for NbN. The primary tool for this investigation is simulations. Computational methods, such as ab initio Molecular Dynamics (AIMD) and the Temperature Dependent Effective Potential (TDEP) method are used to generate phonon spectra and to compute the lattice thermal conductivity. The results indicate that TaN crystal structure stabilizes dynamically at much lower temperatures than previously established with other methods. The average linear thermal expansion coefficient of TaN is a = 9.0 * 10-6 K-1, which is consistent with other TMN. The phonon-phonon lattice thermal conductivity of TaN follows a similar behaviour as for other TMN. Preliminary result for NbN suggests a behaviour at lower temperatures that are similar to that observed for TaN. However, further investigations are required to pinpoint TaN and NbN transition temperatures more exactly and include effects, such as electron-phonon scattering and isotope effects for a better estimation of the lattice thermal conductivity.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:liu-174208 |
| Date | January 2020 |
| Creators | Rydén, Gabriel |
| Publisher | Linköpings universitet, Teoretisk Fysik |
| Source Sets | DiVA Archive at Upsalla University |
| Language | English |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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