We review calculations and measurements of the phonon-dispersion relation of graphite. First-principles calculations using density-functional theory are generally in good agreement with the experimental data since the long-range character of the dynamical matrix is properly taken into account. Calculations with a plane-wave basis demonstrate that for the in-plane optical modes, the generalized-...

A high-frequency optical phonon mode of SrTiO3 (STO) was found to assist the high-temperature superconductivity observed recently at the interface between monolayer FeSe and STO substrate. However, the origin of this mode is not clear. Through first-principles calculations, we find that there is a novel polar phonon mode on the surface layers of the STO substrate, which does not exist in the ST...

A model for phonon heat conduction in a semiconductor nanowire with dimensions comparable to the phonon mean free path is developed. It is based on the solution of Boltzmann’s equation, which takes into account i modification of the acoustic phonon dispersion due to spatial confinement, and ii change in the nonequilibrium phonon distribution due to partially diffuse boundary scattering. Numeric...

The photoluminescence spectra of band-edge transitions in GaN is studied as a function of temperature. The parameters that describe the temperature dependence red-shift of the band-edge transition energy and the broadening of emission line are evaluated using different models. We find that the semi-empirical relation based on phonon-dispersion related spectral function leads to excellent fit to...

Nonlinear probing of the fundamental lattice vibration of polar crystals is shown to reveal insight into higher-order cohesive lattice forces. With a free-electron laser tunable in the far infrared we experimentally investigate the dispersion of the second-order susceptibility due to the phonon resonance in GaAs. We observe a strong resonance enhancement of second harmonic light generation at h...

Gate-modulated low-temperature Raman spectra reveal that the electric field effect (EFE), pervasive in contemporary electronics, has marked impacts on long-wavelength optical phonons of graphene. The EFE in this two-dimensional honeycomb lattice of carbon atoms creates large density modulations of carriers with linear dispersion (known as Dirac fermions). Our EFE Raman spectra display the inter...

Using a numerically determined ground state of the infinite Frenkel-Kontorova chain and the method of real-space Green’s function, we have calculated the phonon dispersion curve of the incommensurate phase of this system. The phonon frequency spectrum exhibits modes with varying degrees of localization ranging from a free-sliding mode to quasiextended and localized modes. Succinct explanations ...

A tight-binding model is fit to first-principles calculations for copper that include structures distorted according to elastic constants and highsymmetry phonon modes. With the resulting model the first-principlesbased phonon dispersion and the free energy are calculated in the quasiharmonic approximation. The resulting thermal expansion, the temperatureand volume-dependence of the elastic con...

In this work we use density functional theory based on the ultra-soft pseudo-potential to calculate thestructural, mechanical and thermal properties of narrow single walled BN, AlN and GaN nanotubes.The electron-electron interactions were expressed within the local density approximation (LDA). Wehave also obtained the Phonon dispersion and elastic constants of these nanotubes using the densityf...