Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 11 of 11 for “"Phonon Dispersions"”.
-
Double resonance Raman spectra of graphene : a full 2D calculation
… Tight binding expressions for both the TO phonon dispersion and the [pi] - [pi]* electronic bands are used, which are then fit to experimental or ab-initio results. We are able to reproduce the single-peak D mode of graphene at ~ 1380 cm-1 that is identical to experiment. A near linear …
-
Structural, vibrational and thermodynamic properties of carbon allotropes from first-principles : diamond, graphite, and nanotubes
… lattice parameters, elastic constants and phonon dispersions and density of states. Very good agreement with available experimental data is found for all these, with the exception of the c/a ratio in graphite and the associated elastic constants and phonon dispersions. Agreement with …
-
X-Ray scattering investigations of subtle ordering in correlated materials
… scattering. We see no change of the acoustic phonon dispersions or of the phonon lifetimes from the HO transition. Calculations of phonon branch contributions to thermal transport suggest that magnetic excitations are responsible for the increase in thermal conductivity in the HO phase. For …
-
Some Aspects of the Crystal Chemistry of Perovskites under High Pressures
… GPa, suggested by the relative enthalpies and phonon dispersions. The elasticities of the Pnma, Imma and I4/mcm structures show mechanical stabilities compatible with the phase transitions. The NH4CdCl3- and CaIrO3-type structures are dynamically stable although not energetically favorable. The …
-
Thermal transport in graphene-based nanostructures and other two-dimensional materials
… or devices with dimensions comparable to the phonon mean free path (MFP). Here, we investigated thermal transport in graphene-based nanostructures and several other 2D materials. First, we measured heat conduction in nanoscale graphene by a substrate-supported thermometry platform. Short, …
-
Structural Study of Heterogeneous States in Lead-free NBT-based Single Crystals
… Diffuse scattering, domain morphology, and phonon dispersions were used to investigate both the static and dynamic properties of these heterogeneous structures.
-
Spectroscopy of Topological Materials and their Technological Applications
… techniques to probe topology and other phonon-related phenomena in materials and by investigating potential applications of topological materials in modern-day technologies. We begin the dissertation by illustrating a chronicle of research into topology in condensed matter physics over …
-
X-ray Studies of Lattice Dynamics
… has recently shown great promise as a tool for phonon studies, complementing more traditional neutron scattering techniques. Quasi-elastic x-ray scattering from thermally populated phonon modes has been used to study lattice dynamics and phonon phase transitions in several systems. Several …
-
Resonant Raman scattering in graphene
… by using state-of-the-art electronic [5] and iTO phonon dispersions [6] fit to ab initio GW calculations. For the first time in the literature we include the variation of the light-matter and electron-phonon interaction matrix elements calculated via an ab initio density functional theory (DFT) …
-
Lattice Dynamics in Temperature-driven and Photo-induced Phase Transitions
… the nearly complete measurement of anharmonic phonon behaviors near phase transitions. It is difficult to explain the observed effects of phonon anharmonicity without using first-principles calculations, for instance to obtain renormalized second- order and higher-order force-constants. …
-
A theoretical study of molecular crystals
… of the infrared- and/or Raman-active vibrations, phonon dispersions, and inelastic neutron scattering (INS) were calculated. A systematic hierarchy of methods was applied from Hartree–Fock (HF) to coupled-cluster singles and doubles (CCSD), as well as combining the aug-cc-pVDZ and aug-cc-pVTZ …