NSLS-II Seminar

Over the past few years our group has focused a large experimental and theoretical effort on quantifying the vibrational energies in metals at high-pressures and high-temperatures. Our interest in the high-pressure properties of these elements is motivated both by their importance as constituents in the cores of many planetary bodies and by the rich variety of intriguing phenomena displayed by their lattice dynamics at room pressure. While IXS has addressed a number of phenomenological problems of great importance, such as the nature of the acoustic anisotropy of the Earth’s inner core by direct measurements on the high-pressure hcp-phase of iron, as well as by proxy experiments on cobalt; we have also pursued more general studies of condensed matter at high-pressure aimed at understanding many fundamental physical properties in systems as varied as Fe, Co, Mo, Ta, V, Ce, and even Pu. Indeed, with the application of pressures approaching 100 GPa, we are able to perturb the energy of condensed systems on the order of ~1 eV. Thus, performing lattice dynamics measurements under these conditions allows us to probe systems that have undergone fundamental changes the energetics of the chemical bonds. Most recently, we have determined the phonon dispersions across the isostructural gamma- to alpha-cerium transition, one of the most intriguing elemental phase transitions. Our new data together with first principals calculations place important thermodynamical and theoretical constraints on the underlying physics of this important transition. Such experiments have now begun to shed light on important magneto-elastic interactions, electron-phonon coupling and have the singular potential to provide critical data on the newly observed elastic perturbations across pressure induced spin-transitions.

If you would like to meet with these speakers after this presentation, please contact the host at cai@bnl.gov prior to this presentation to coordinate a time slot.