Inelastic Neutron Scattering and Density Functional Theory–Molecular Dynamics Study of Si Dynamics in Ti3SiC2 |
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| Authors: | Gordon J. Kearley Veronica Gray Daniel P. Riley Oliver Kirstein Ramzi Kutteh Erich H. Kisi |
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| Affiliation: | 1. The Bragg Institute, Australian Nuclear Science and Technology Organisation, , Lucas Heights, New South Wales, 2234 Australia;2. School of Engineering, The University of Newcastle, , Callaghan, New South Wales, 2308 Australia;3. Institute of Materials Engineering (IME), Australian Nuclear Science and Technology Organisation, , Lucas Heights, New South Wales, 2234 Australia;4. European Spallation Source (ESS) AB, , Lund, 22100 Sweden;5. School of Physics, University of Sydney, , Sydney, New South Wales, 2006 Australia |
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| Abstract: | Observed differences between measured and calculated elastic constants for Ti3SiC2 are investigated using Density Functional Theory and Inelastic Neutron Scattering. The agreement between the calculated lattice dynamics and the dynamics measured by inelastic neutron scattering is considered good except at energies below ~20 meV where discrepancies suggest anharmonic potentials. This suggestion is confirmed by Density Functional Theory—Molecular Dynamics simulation which shows multiple site occupancy of the Si atoms within the basal plane at finite temperature and produces a calculated inelastic spectrum in better agreement with the measured spectrum in the low‐energy region. The highly anharmonic potential energy surface of the Si atoms offers an explanation for the failure of elastic constants, calculated based on the harmonic approximation, to agree with initial experimental measurements. |
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