HiPSEC Students Seminar

The High Pressure Science and Engineering Center meets every Wednesday in the BPB conference room at 11:30 AM. We typically have a scientific talk, short reports on students’ attendance of conferences and workshops and general discussions. We welcome anyone interested in learning about high pressure science in general and about HiPSEC in particular to attend our meetings.

Upcoming talks


Wednesday, Feb 8, 11:30 am, BPB 217

Recreating planetary cores in the laboratory

Daniel Sneed

HiPSEC, UNLV

Of the different planets in our solar system, our giant icy neighbors Neptune and Uranus are extremely fascinating, Uranus being the more peculiar of the two. Though Uranus is almost 2 billion kilometers closer to the sun than Neptune, its average surface temperature can dip as low as 50 K, actually making it colder than Neptune. The primary belief for this is that the core of Uranus, which is believed to be made of diamond, silicates, iron, and nickel, has shed most of its energy; cooling down to a point where it no longer radiates much heat. Despite having a cold core, Uranus has a very active and unique magnetic field. Unlike Earth, whose magnetic field is driven by a very hot active core, it is believed that Uranus’s unique magnetic field is actually driven by mixtures of super ionic and metallic molecular compounds. It has been measured that the primary components of its mantle are water, ammonia, and methane, which have all been predicted to show superionic properties at the conditions present within the mantle. There have recently been efforts in attempting to recreate the conditions necessary to verify these predicted phases, primarily in the area of shock compression. This is difficult as the region of P-T space that these superionic phases exist cannot be reached by traditional shock compression. In a traditional shock experiment the path the hugoniot takes overshoots the targeted region due to high amounts of entropy generated, so very high temperatures are reached along with very high pressures. One way around this is by compressing the sample to a specific density prior to shocking in order to take off hugoniot shock paths, reaching the pressures necessary at much lower temperatures. I will discuss some details of how these pre-compressed experiments are performed as well as how Velocity Interferometry for Any Reflector (VISAR) is used to interpret the results.


Wednesday, Jan 18, 11:30 am, BPB 217

Adventures with 5d orbitals at high pressure

Daniel Haskel

Advanced Photon Source, Argonne National Laboratory

While first-row (3d) transition metal (TM) oxides continue to provide a rich playground for studies of electron correlations, recent focus has shifted to third-row (5d) TM oxides in the search for novel quantum states. The sizable spin-orbit interaction in heavy 5d ions, coupled with reduced on-site Coulomb interactions as a result of the large spatial extent of 5d orbitals, create unique experimental and theoretical opportunities for discovery of new electronic phases of matter.

We have studied some of the consequences of enhanced S-O coupling and spatial extent of 5d orbitals on the electronic structure and magnetic (exchange) interactions in a novel “iridate” magnetic insulator, Sr2IrO4. The high-brilliance, penetration power, and polarization/energy tunability of synchrotron radiation enable the use of x-ray absorption spectroscopy (including circular dichroism) and resonant magnetic scattering techniques in the diamond anvil cell providing exquisite sensitivity to the evolution of electronic correlations at high pressure. Among other findings, we discovered that pressure leads to frustration of exchange interactions in the square lattice of entangled spin-orbital Iridium moments and emergence of quantum paramagnetism, possibly a quantum spin liquid phase.

Higher brilliance, 4th generation synchrotron light sources now in development around the globe will bring unprecedented opportunities for studies of electronic/magnetic order at the limit of static high-pressure generation technologies.

Work at Argonne is supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC-02-06CH11357.

 


Wednesday, Dec 14, 11:30 am, BPB 217

Laser Driven Shock and the Measurement of Velocity and Temperature

Chris Higgins

HiPSEC, UNLV

Laser driven shock experiments allow exploration of a high pressure and temperature phase space relative to static compression experiments. With the recent discovery of exoplanets, many questions have risen as to the details of the exterior and interior of these planets. We intend to investigate this phase space in order to further explore the compositions and details of these terrestrial systems. The data analysis of these experiments can be quite complex, and newer methods are continuously evolving to better interpret the data that is being collected. A recent collaboration with Lawrence Livermore National Laboratory and the Omega Laser Facility has given access to facilities and data not easily obtained by conventional gas-gun methods. We intend to explore the methods of experimentation and data analysis that will be used at these facilities for both past and future work.


 

Wednesday, Nov. 2, 11:30 AM, BPB 217

Community Extreme Tonnage User Service (CETUS): Progress on the 5000 ton press facility and partnership opportunities for UNLV

Lisa Danielson

Manager, Basic and Applied Research: Jacobs, JETS


Wednesday, Oct. 12, 11:30 AM, BPB 217

Structure Prediction from Perfect Crystals to Defects

Qiang Zhu

 HiPSEC, UNLV

Nowadays, the urgent demand for new technologies has greatly exceeds the capabilities of materials research. Understanding the atomic structure of a material is the first step in materials design. We have developed a method to enable the accurate prediction of structures form only a few information for a given materials, based on evolutionary global optimization method and Density Functional Theory (DFT) calculations. In this talk, I will discuss some recent progresses in discovering materials with novel stoichiometry under high pressure and studying the polymorphism of organic crystals. Furthermore, the initial attempts to predict materials defects will be briefly discussed.


Wednesday, Oct. 5, 11:30 AM, BPB 217

 Aluminum: A pretty good metal

William Wolfs

Aluminum’s material properties are, taken by themselves, fairly unremarkable.  However, its remarkable combination of density, hardness, conductivity and phase stability make it ideal for a number of structural and electronic applications in modern technology.  Additionally, it alloys well with titanium to create a number of workhouse materials, and its behavior in alloy conditions is a subject of active research.


Friday, Sept. 30, 3:30 PM, BPB 102

The Reach of High Pressure Research in the Spallation Neutron Source

António M. dos Santos

Quantum Condensed Matter Division, Oak Ridge National Laboratory

The intrinsic properties of neutrons and the way these interact with matter, make neutron scattering an exceptional tool in materials research, allowing studies on problems mostly inaccessible through other techniques. These include structural studies of compounds combining heavy and light elements, the determination of the magnetic structure of materials, the non-destructive testing of engineering parts and the probing of crystal dynamics, both structural and magnetic. The SNAP instrument (Spallation Neutrons and Pressure) a neutron diffractometer dedicated to the study of materials under high pressure that is part of the SNS’s suite of instruments has pioneered the revival of high pressure neutron diffraction. Since it began operating, a broad range of materials systems have been investigated, in the form of powders, glasses and single crystals. Here we will present some recent scientific results of research performed at SNAP, along with ongoing improvements and additions to the SNAP capabilities. Finally, some examples will be used to illustrate how other neutron techniques can provide valuable insight in the context of physics and materials science.


Friday, Sept 16th in BPB 217 3:30pm

Nuclear resonant and inelastic x-ray scattering studies under high pressure

Esen Ercan Alp

Advanced Photon Source,Argonne National Laboratory

Nuclear resonant scattering (NRS) and inelastic x-ray scattering (IXS) studies under high pressure continues to be very popular among geophysics and mineral physics researchers. At present, Advanced Phonon Source has two dedicated beamlines for high- energy resolution (1-2 meV) IXS studies (Sector 3 and 30). Additional capabilities exist at Sector 16 for NRS studies.

  I will present new results on Fe, Sn, Eu and Dy based nuclear resonant studies, including isotope fractionation measurements in iron and tin compounds, kinetics of phase transformations under varying temperature and pressure in iron, europium and dysprosium metals. I will highlight the use of APS Hybrid mode for synchrotron Mössbauer Spectroscopy and I will point out some of the expected changes in the near future.


Wednesday, Aug. 31, 11:30 AM, BPB 217

Liping Wang

Large-Volume Press (LVP) Lab in HiPSEC

In this talk I will provide an update on the status of HiPSEC’s Large-Volume Press (LVP) lab.  The installation of all necessary components has been completed, and the automation system for compression and decompression has been fully tested. Pressures have been calibrated against loading forces at room temperature using in-situ electrical resistance measurements on Bi, PbS, PbTe, and ZnTe. The calibrations at high temperature (1200 C) are being carried out at this moment. The LVP Lab is expected to be fully functional within a few weeks and ready to serve entire group at HiPSEC.


Friday, Sept. 16, 3:45 PM, BPB 217

Esen Ercan Alp

 (Advanced Photon Source, Argonne National Laboratory, Argonne Illinois 60439

Nuclear resonant and inelastic x-ray scattering studies under high pressure

Nuclear resonant scattering (NRS) and inelastic x-ray scattering (IXS) studies under high pressure continues to be very popular among geophysics and mineral physics researchers. At present, Advanced Phonon Source has two dedicated beamlines for high- energy resolution (1-2 meV) IXS studies (Sector 3 and 30). Additional capabilities exist at Sector 16 for NRS studies.

I will present new results on Fe, Sn, Eu and Dy based nuclear resonant studies, including isotope fractionation measurements in iron and tin compounds, kinetics of phase transformations under varying temperature and pressure in iron, europium and dysprosium metals. I will highlight the use of APS Hybrid mode for synchrotron Mössbauer Spectroscopy and I will point out some of the expected changes in the near future.

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This work is supported by U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences under contract DE-AC02-06CH11357, and the Consortium for Materials Properties Research in Earth Sciences (COMPRES) [National Science Foundation (NSF) EAR 06-49658].



attendance sheet