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 20 of 33 for “"Phonon Dispersion"”.
-
Phonon Dispersion Relations in Chrystals
… from a single crystal enables us to deduce the phonon dispersion relation, that is the frequency of the normal modes as a function of their wave vectors. These experiments provide a far more direct test of theories of crystal dynamics than do specific heat measurements. The possibility of …
-
Phonon dispersion curves and atomic mean square displacement for several fcc and bcc materials
The atomic mean square displacement (MSD) and the phonon dispersion curves (PDC's) of a number of face-centred cubic (fcc) and body-centred cubic (bcc) materials have been calclllated from the quasiharmonic (QH) theory, the lowest order (A2 ) perturbation theory (PT) and a recently proposed Green's …
-
X-ray thermal diffuse scattering and its studies of lattice dynamics
… by people in experimental determination of phonon dispersion relations. With the advent of synchrotron radiation technology, it has reemerged as an efficient probe for phonon studies in the recent decade. The scattering can be described with a semi-classical theory, and is often decomposed …
-
Hypersonic phononic crystals
Manipulation of the distribution of phonons inM a solid is important for both basic science and applications ranging from heat management to reduction of noise in electronic circuits and creating materials with superior acoustic and acousto-optical properties. This thesis explores hypersonic …
-
Thermal properties of graphene
… and the direction of dissipation of heat flux. Phonon dispersion spectra are presented for these structures using Materials Studio. Non- Equilibrium Molecular Dynamics simulation has been implemented for the calculations. Structures of doped graphene are modeled using Density Functional Theory …
-
Phonon spectra and thermal properties of some fcc metals using embedded-atom potentials /
… we have calculated the dynamical matrices and phonon dispersion curves for six fee metals (Cu,Ag,Au,Ni,Pd and Pt). We have also investigated, within the quasiharmonic approximation, some other thermal properties of these metals which depend on the phonon density of states, such as the …
-
Thermal transport in low dimensional semiconductor nanostructures
… DFT, the interatomic force constants and the phonon dispersion relations were calculated using DFPT as implemented in Quantum Espresso. In order to fundamentally understand the effect of atomic arrangements, we calculated the phonon conductance in a ballistic approach using a Green's function …
-
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 …
-
ATOMISTIC MODELING OF PHONON BANDSTRUCTURE AND TRANSPORT FOR OPTIMAL THERMAL MANAGEMENT IN NANOSCALE DEVICES
… approach predominantly uses empirically fitted phonon dispersion relations as input to determine the properties of phonons so as to predict the thermal conductivity of specified material geometry. The empirically fitted dispersion relations assume harmonic approximation thereby failing to …
-
Photophysics of carbon nanotubes
… exhibit dramatic changes in their electron and phonon dispersion relations due to the curvature of the nanotube sidewall and the enhanced electron correlation effects associated with one dimensionality. The optical transition energies in small-diameter carbon nanotubes show a strong dependence …
-
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 …
-
X-ray Debye temperatures of solid neon
… with Debye temperatures obtained from neutron phonon dispersion measurements, and are in general agreement with other thermodynamic data on solid neon. However, the values of eM and eM' obtained in this work do not agree with published quasiharmonic or anharmonic theories, especially at high …
-
The X-ray Debye temperature of solid krypton
… measurements, entropy measurements, and neutron phonon dispersion measurements. On the other hand, the results of the present experiment disagree sharply with two previous experiments based on the Mossbauereffect, implying that there was some difficulty inherent in the Mossbauer methods. The high …
-
Studies of structure and dynamics of biological macro-molecular assemblies by low angle neutron diffraction and inelastic X-ray scattering
… dynamic structure factor measured with IXS, the phonon dispersion relations of 40 wt% calf-thymus Na-DNA with different counterion atmosphere are constructed. It is found that the addition of extra counterions will increase phonon damping at small scattering wave vector, Q. At the intermediate Q …
-
Nanoscale thermal transport for biological and physical applications
… to a serious thermal management challenge. The phonon thermal conductivity is an important material property because of its role in thermal energy transport in semiconductors. A higher thermal conductivity material is capable of removing more heat since higher frequency phonons are able to …
-
Atomistic simulation of strength and deformation of ceramic materials
… of Ewald summation to a binary ionic lattice for phonon dispersion, elastic constant, and heat current calculations, and a stand-alone scheme for coupled MD-continuum simulations based on domain decomposition and control feedback. The onset of structural instability in MD simulation of an …
-
Applications of lattice dynamics theory : calculating vibrational entropy in alloys and dielectric losses in ceramics
… terms of anharmonic forces, atomic masses, and phonon dispersion curves.
-
Simulation of Thermal Effects in Semiconductor Materials and Devices
… to describe the behavior of both electrons and phonons and their interaction with each other, as well as their interaction with external potentials by coupling the transport equations with the Poisson equation. Several methods of solving the transport equations and simulating charge and thermal …
-
Study of phonon transmission through solid-solid interfaces and superlattices by phonon imaging
… the low-temperature propagation of heat pulses (phonons) through crystals and across solid-solid interfaces. The phonon imaging technique has been used to examine the angular and temporal dependence of the phonon-flux intensity in several systems, listed below. 1. Phonon focusing in cubic …
-
A deviational Monte Carlo formulation of ab initio phonon transport and its application to the study of kinetic effects in graphene ribbons
… method for solving the Boltzmann equation for phonon transport subject to the linearized ab initio 3-phonon scattering operator. Phonon dispersion relations and transition rates are obtained from density functional theory calculations. The ab initio scattering operator replaces the commonly …
Page 1 of 2