This is a past event.

Physics Colloquium will take place at 4 p.m. Thursday (Oct. 19th) in Fisher 139. Dr. Hector Lorenzana will present "In Situ Probing of the Lattice Response of the Solid at High Pressures".

This presentation will touch upon two areas: (a) studies of the real-time, dynamic response of the shocked solid and (b) static, high-pressure investigations of novel phase transformations and chemical changes that are recoverable at ambient conditions. AREA A: Understanding the dynamic lattice response of solids under the extreme conditions of pressure, temperature and strain rate is a scientific quest that spans nearly a century.  Critical to developing this understanding is the ability to probe and model the spatial and temporal evolution of the material microstructure and properties at the scale of the relevant physical phenomena—nanometers to micrometers and picoseconds to nanoseconds. Experimental investigations over this range of spatial and temporal scales have become feasible only in the last decade or so. The equivalent advancements in simulation capabilities now mean that we can conduct simulations and experiments at overlapping temporal and spatial scales. In this presentation, we describe some of our studies which exploit existing and new generation ultra-bright, ultrafast x-ray sources to investigate the real-time physical phenomena that control the dynamic response of shocked materials. AREA B: There are many examples of materials that have been created at high-pressures but are metastable at ambient conditions, diamond probably being the most well-known. Seeking new materials with potential technological applications, we describe experiments aimed at synthesizing novel material forms under extreme temperatures and pressures, with the goal of recovering them down to ambient conditions. 

Dr. Lorenzana received his A.B. and Ph.D. degrees both in physics from Harvard University and was awarded a University of California President’s Fellowship at the Berkeley in 1990. He pursued static high-pressure studies of gases in the UCB Geophysics Department and was hired at the Lawrence Livermore National Laboratory (LLNL) in 1992, where he initiated an effort to study phase transformations and chemical reactivity of first row elements at static high pressures. He has led a LLNL Strategic Initiative to explore materials properties under shock compression as well as a large theoretical and experimental materials effort to develop constitutive models that encapsulate dynamic materials behavior. In pursuit of these research goals, Dr. Lorenzana has served at various times as group leader, Deputy Division Leader, as well as Materials Program Lead in the Physical and Life Sciences Directorate at LLNL.