Graeme J. Ackland, Head of Institute of Condensed Matter and Complex Systems, University of Edinburgh, UK visited ISSP on Jan 21st. He was warmly welcomed by ISSP co-director Prof. Zhi Zeng and director of CEMEE Dr. Xiaojia Chen.
Prof. Ackland gave a lecture on "Solid Hydrogen at High Pressure Raman Spectra from Molecular Dynamics". He introduced the structure of solid hydrogen at different pressure in the experimental and theoretical studies. Using Molecule Dynamics Method, the Raman modes of hydrogen under pressure are calculated and the result are applied in the HD system (PRL 113, 175501 (2014). For the Raman spectra above 300Gpa, the Anderson localization is introduced to understand the phase IV and V of hydrogen. For the determination of the structure and dynamical properties of Hydrogen of Phase IV, this has been identified only in spectroscopy experiments and in theoretical calculations. Together, these present a picture of a complicated crystal structure in which the molecule areon the verge of stability. The low symmetry structure is a way of lowering the free energy of the material, and avoiding metallization.
Professor Graeme Ackland is a condensed matter physicist who is using theoretical calculations based on electronic structure calculations and molecular dynamics to study the matter at extreme conditions. He has quite a wide range of interests which include the behaviour of solid hydrogen at very high pressures in a wide temperature range, behaviour of industrially interesting metals such astitanium alloys during the machining and understanding of the complex structures of simple elements which are encountered at high pressures.