Pressure-induced change of effective Coulomb interaction in superconducting yttrium

摘要: This thesis presents a theoretical study of materials under high pressure using ab initio lattice dynamics based on density functional theory and perturbation both super-cell linear response approach. Ab approach is applied to compare our predictions with experimental findings. Phonon dispersion curves fcc α-γ cerium are calculated compared inelastic X-ray scattering data. Pressure dependency phonon states in two cubic phases TiO2 allows us assign the observed phase experiments be fluorite rather than pyrite structure. Dynamical stability cotunnite at low can explain quenching phenomena experiments. Our O2 vibron mode e-ζ solid oxygen supports hypothesis that iso-structural. Hydrogen-dense attract great attention not only because they open path related metallization (superconductivity) hydrogen but also closely important industrial applications (hydrogen storage). Using method, we find metallic fcc-AlH3 dynamically stabilized range 72-106 GPa persist ambient if finite temperature effects considered. For SiH4, test dynamical stability, Raman spectra, zero point energy, utilize GW calculations for self energy correction. We tetragonal SiH4 assigned experimentally one. predict fcc-YH3 pressure-induced superconductor transition 40 K 17.7 GPa. With increasing this material undergoes superconductor-metal-superconductor underlying mechanism simultaneously explains metal-insulator 25 YH3-δ.