Related papers: Phonon anharmonicity and negative thermal expansio…
We use a symmetry-motivated approach to analyse neutron pair distribution function data to investigate the mechanism of negative thermal expansion (NTE) in ReO$_3$. This analysis shows that the local structure of ReO$_3$ is dominated by an…
We describe nonlinear phonon-thermoelectric devices where charge current and electronic and phononic heat currents are coupled, driven by voltage and temperature biases, when phonon-assisted inelastic processes dominate the transport. Our…
Understanding the anharmonic phonon properties of crystal compounds -- such as phonon lifetimes and thermal conductivities -- is essential for investigating and optimizing their thermal transport behaviors. These properties also impact…
We have used neutron scattering techniques to characterize the diffuse scattering and lattice dynamics in single crystals of the relaxor PMN from 10K to 900K. We observed two distinct types of diffuse scattering. The first is weak,…
We have used ab-initio density functional theory technique to understand the phase transitions and structural changes in various high temperature/pressure phases of LiAlO2. The electronic band structure as well as phonon spectra are…
Cold neutron scattering experiments have been performed to explore the energy, temperature, and wave-vector dependence of the diffuse scattering and the transverse acoustic (TA) phonons in the relaxor PbMg(1/3)Nb(2/3)O3. We have observed a…
Negative thermal expansion (NTE) - the phenomenon where some materials shrink rather than expand when heated - is both intriguing and useful, but remains poorly understood. Current understanding hinges on the role of specific vibrational…
We conduct first-principles theoretical studies to investigate the temperature-dependent phonon properties of orthorhombic SrZrO$_3$ (SZO) perovskite. Our calculations include the quasiharmonic approximation, in which we explored mode…
A first-principles-based method for computing phonons of magnetic random solid solutions including thermal magnetic fluctuations is developed. The method takes fluctuations of force constants (FCs) due to magnetic excitations as well as due…
We derive a compact matrix expression for the linear thermal expansion coefficients (TECs) for a general orthorhombic system which relates the elastic properties and the integrated quantities based on deformation and mode dependent…
The thermal expansion behavior of metal fluorides can be tuned by choosing appropriate metal cation. We present ab-initio lattice dynamical studies on the metal fluorides (CaZrF6, MgZrF6 and SrZrF6) and identify the anharmonic phonon modes…
Pressure and temperature dependence of the negative thermal expansion in Zn(CN)$_2$ is fully investigated using molecular dynamics simulations with a built potential model. The advantage of this study allows us to reproduce all the exotic…
The first order standard perturbation theory combined with ab initio projector augmented wave operator challenges the realization of the standard Sternheimer equation with linear computational efficiency. This efficiency motivates us to…
Nanoscale defects such as dislocations, have a significant impact on the phonon thermal transport properties in non-metallic materials. To unravel these effects, understanding of defect phonon modes is essential. Herein, at the atomic…
Amorphous solids manifest puzzling effects of mysterious degrees of freedom that give rise to a heat capacity and phonon scattering in great excess over what would be expected for a solid that has a unique vibrational ground state. Of…
Prior experimental studies showed that nanowires are promising structures for improving the thermoelectric performance of practical thermoelectric materials due to the strongly induced phonon-boundary scattering. However, few studies…
The current noise density S of a conductor in equilibrium, the Johnson noise, is determined by its temperature T: S=4kTG with G the conductance. The sample's noise temperature Tn=S/(4kG) generalizes T for a system out of equilibrium. We…
Predictions of the anisotropic coefficients of thermal expansion are needed to not only compare to experimental measurement, but also as input for macroscopic modeling of devices which operate over a large temperature range. While most…
We present a study of the soft transverse optic phonon mode in SnTe in comparison to the corresponding mode in PbTe using inelastic neutron scattering and ab-initio lattice dynamical calculations. In contrast to previous reports our…
Phonons, the quantum mechanical representation of lattice vibrations, and their coupling to the electronic degrees of freedom are important for understanding thermal and electric properties of materials. For the first time, phonons have…