Date of Award
Doctor of Philosophy
Dr. Clement Burns
Dr. Arthur McGurn
Dr. Thomas Gorczyca
Dr. Ayman Said
Quantum phase transition, ab initio method, x-ray scattering, high resolution, high pressure, quantum ESPRESSO
In this project, inelastic x-ray scattering (IXS) was used to measure the phonon dispersion in chromium at high pressure and low temperature, and an ab initio method was used to simulate the phonon dispersion with different lattice constants and magnetic orders. The IXS measurements were carried out in Sector 30 at the Advanced Photon Source at Argonne National Laboratory. Data were taken at room temperature with pressures of 1.29 GPa, 8.15 GPa, 10.6 GPa, and at 5 K with a pressure of 18.36 GPa. The data shows similar phonon behavior in the antiferromagnetism (AFM) and the spin density wave (SDW) states at room temperature, but different phonon behavior at 5 K and 18.6 GPa. The ab initio simulation was used to calculate the phonon dispersion with AFM plus SDW at the lattice constant corresponding to the measured pressure in the experiment. By comparing the experimental data and the simulation result, it seems likely that a new state exists after the quantum phase transition.
Li, Chengyang, "Studies of the Quantum Phase Transition in Chromium Using Inelastic X-Ray Scattering and Ab Initio Methods" (2014). Dissertations. 284.