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Friday, October 14, 2011, 2:30PM, BPB 217
Physics Colloquium
Dr. Surendra K. Saxena
Florida International University

Materials at Extreme Conditions: Experiments and Thermodynamic Modeling

The results of several experiments on laser heating of solids, particularly iron, will be discussed in this talk along with thermodynamic modeling of solid properties at extreme conditions. CeSMEC facilities will be briefly described.

Problems with thermodynamic modeling of solids at extreme conditions arise due to lack of a suitable EoS for solids and melts. While several theory based models such as the Birch Murnaghan or the Vinet can be used for the pressure-volume data, the effect of temperature on volume presents difficulties. Pressure-volume-temperature data on several solids will be used to discuss the problem and some possible solutions which will permit us to obtain complete thermodynamic data (heat capacity and entropy) at extreme conditions. The iron phase diagram has gone through number of revisions but several problems remain. The experimental data on pressure-volume-temperature (PVT), melting and thermal conductivity will be reviewed. The discussion will include the location of possible new triple points, the computer simulated high P-T BCC phase, and the melting curve. The computational as well as the experimental data will be used to present an internally consistent model of iron to constrain the phase diagram to core conditions. A triple point may be located at a temperature of 4386 K and a pressure of 191GPa). The pure iron inner core temperature is 6517 K at 364 GPa with a density of 13.705 which is denser than the PREM model density by 7.5%. If Ni has to be mixed with iron because of cosmochemical consideration (composition of iron meteorite), a lot more of a lower density element S, Si or O will have to be in solid solution to lower the density of the inner core causing the temperature of the inner core to drop by several hundred degrees. Thus 6517 K is the absolute upper temperature of the inner core. The density of the liquid iron in the outer core conditions is 7.60% (top) to 9.66% (bottom) higher in density than the PREM model density. Again a mixing of the light element would bring down the melting as well as the adiabatic temperature and therefore the temperature of 4750 K is the absolute upper temperature at the top of the outer core. A lowering of the temperature to 3950 ± 200 K as estimated by Van der Hilst et al. is possible. The average heat capacity of a pure iron inner core is 27.24 J/mol, yielding the heat content of 155.17 x10 21 joules for the iron core (mass of inner core 102x1021 Kg). (all numbers likely to change with further processing).

Friday, October 7, 2011, 3:45PM, BPB 217 (refreshments @ 3:30)
Physics Colloquium
Professor Haozhe Liu
Harbin Institute of Technology, Harbin, China

Synchrotron X-ray Diffraction Studies for Phase Transitions under High Pressure Conditions

In this presentation, the joint effort from multiple institutions for HIT (Harbin Institute of Technology) Oversea Collaborative Base Program at Argonne National Laboratory (ANL) and Brookhaven National Laboratory (BNL) will be introduced. This program offers great opportunity for training young faculty and students in HIT as exchanging scholar in synchrotron facilities of ANL and BNL, and brings new projects and new insight for deeper understanding on phase transition behaviors of materials under high pressure extreme conditions. Several projects with fresh data and results will be presented, including a new type of disordered substitution alloy structural model for the puzzling high pressure phase of topological insulator Sb2Te3, phase diagram for superconducting material EuFe2As2 under high pressure and low temperature domain, and diffraction tomography development in diamond anvil cell environment for phase transitions researches.

Tuesday, September 20, 2011
NSTec Visit Agenda
NSTec Scientists/Managers and Dr. Reinhard Boehler Visit UNLV/HiPSEC
9:00 am
Pick visitors up from hotel Hyatt Place and transport to UNLV Physics – Yusheng Zhao and Oliver Tsauner
9:15 am
Continental Breakfast – BPB-217
9:45 am
UNLV Welcome Speech – Timothy L. Porter, Dean, College of Sciences
10:00 am
NSTec / LANL – Dr. Rob Hixson, Melting Puzzle at Dynamic/Static High P-Ts
11:00 am
CIW / EFree – Dr. Reinhard Boehler, Laser Heating for DAC Experiments
12:00 pm
Lunch Break – BPB-217 and HiPSEC Director Zhao will brief HiPSEC scope and structure. UNLV Faculty and Staff will brief their research capability and activity
1:30 pm
NSTec SDRD Director Howard Bender, Site-Directed Research and Development (SDRD) Overview and Opportunities
2:15 pm
Andrew Cornelius, High Pressure Studies on Strongly Correlated d- f-Electron Systems
3:00 pm
NSTec Diagnostic Instrumentation Manager, David L. Esquibel, Shock Wave Related Diagnostic Development and classes of Experiments Supported on the Major Stockpile Platforms
3:45 pm
Oliver Tschauner, Materials Deformation and Shock Recovery Experiments
4:30 pm
Round table discussion
5:00 pm
Transportation of visitors to hotel – Liping Wang / Valentine Iota
6:30 pm
Dinner gathering
July 21, 2011, 1:30PM, SEB 2251
Master's Thesis Presentation
Makram Abd El Qader
Department of Electrical and Computer Engineering

Structural, Electrical and Thermoelectric Properties of CrSi2 Thin Films

The world’s demand for more reliable and safe energy sources is causing drastic escalation of social and political unrest. Worldwide governments are increasing the efforts in research and development for more sustainable energy solutions. Such efforts are to prevent the environmental impact of global climate change due to the combustion of fossil fuels, which is becoming increasingly alarming. Approximately 90% of the world’s electricity is produced by heat energy as a result of burning fossil fuels. Production plants typically operate at 30-40 percent efficiency, loosing around 15 terawatts of power in the form of heat to the environment. Thermoelectric power generators can convert some of this waste heat into useful power. Residential heating, automotive exhaust, and industrial processes all generate enormous amount of heat that could be converted to electricity by thermoelectric modules. Thermoelectric devices are potential power sources due to their direct conversion of thermal gradients into electric current.

Materials with good thermoelectric properties are the main focus of the modern technology because of their potential use in thermoelectric applications such as cooling systems. Among the potential semiconducting silicides, CrSi2 is attractive because of its high thermal and chemical stability and its potential for thermoelectric application. CrSi2/SiO2 structures were prepared using rf sputtering. These structures (as grown and annealed) were characterized using X-ray diffraction to study crystal structure, SEM-EDAX to study the composition, and lab built resistivity and Seebeck apparatuses to study thermoelectric properties. Dependence of the measured properties on the thickness of CrSi2, temperature and time of annealing are presented and discussed. Also the design and assembly of new lab built three gun sputtering system is discussed. The system has the capabilities to deposit multiple layers from three different materials in nano-dimensional structures. This system will enable research groups from various departments to fabricate complex materials structures with a complete control over process conditions and composition of ternary (three element) thin-Films prepared for optical, electronic and thermo-electric applications.

June 21, 2011, 3:00PM, BPB 217 (refreshments @ 2:45)
Physics Colloquium
Prof. Brian Maple
University of California, San Diego

High-Pressure Studies of Strongly Correlated Electron Phenomena in Novel Materials

Complex multinary d- and f-electron compounds have proven to be a rich reservoir of strongly correlated electron ground states and phenomena: e.g., valence fluctuations, hybridization gap semiconductivity, heavy fermion and non-Fermi liquid behavior, quantum criticality, unconventional superconductivity in which electrons are paired in states with non-zero angular momentum, high temperature superconductivity, magnetic order, coexistence of superconductivity and magnetic order, quadrupolar order, etc. In these materials, the occurrence of such a wide range of ground states and phenomena arises from a delicate interplay between competing interactions that can be tuned by chemical substitution, as well as the application of pressure and magnetic fields, resulting in complex electronic phase diagrams in the hyperspace of temperature, chemical composition, pressure and magnetic field. In this talk, we review selected examples in which pressure has been employed as a tuning parameter to access and study various strongly correlated electron phenomena in novel d- and f-electron materials. Phenomena of particular interest include unconventional superconductivity, high temperature superconductivity, magnetic and quadru-polar order, charge and spin density waves, quantum critical behavior, heavy fermion behavior and non-Fermi liquid behavior. The support of the US NNSA, DOE and NSF is gratefully acknowledged.

May 16, 2011
Adam Simon has been awarded the 2010 Distinguished Teaching Award from the UNLV College of Sciences.
May 7, 2011, 10AM-7PM, Cashman Center
Snapshots from the Festival
HiPSEC scientists and students will participate in the Las Vegas Science Expo


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April 28, 2011, 3:00PM, SEB 1243
HiPSEC Colloquium
Dr. Dan Farber
Lawrence Livermore Nation Laboratory

Lattice Dynamics at Ultra-High Pressures: Quantification of Phonon Energies Using High-Resolution Inelastic X-Ray Scattering
March 29, 2011, 3:00PM, BPB 217
Physics Colloquium
Professor Choong-Shik Yoo
Washington State University, Pullman

Novel Phases Under Extreme Static and Dynamic Conditions
March 28, 2011, BPB 217
Chinese Academy of Sciences/Institute of Physics Visit
10:10 am
CAS/IOP Introduction -- Director Yupeng Wang
10:45 am
IOP Talk 1: Effects of pressure on iron pnictide superconductors -- Changqing Jin
11:30 am
IOP Talk 2: Topological Insulators: from basic science to materials design -- Zhong Fang
12:30 pm
HiPSEC Introduction -- Executive Director Yusheng Zhao
1:30 pm
HiPSEC Talk 1: High Pressure Studies on Strongly Correlated d- f-Electron Systems -- Andrew Cornelius
2:15 pm
HiPSEC Talk 2: Pressure-induced Elastic Anomalies in Lanthanide Metals -- Oliver Tschauner
3:00 pm
HiPSEC Talk 3: Research on Highly Compressed States of Matter: Advanced Material Design, Modeling, Synthesis and Characterization -- Changfeng Chen
March 11, 2011, 11:00AM, BPB 217
Professor Jianjun Dong
Auburn University

Theory and Simulations of Lattice Thermal Conductivity for Applications in Materials and Geological Sciences

Lattice thermal conduction is the dominant mechanism for heat transport inside an optically opaque and electrically insulating solid, despite rapid developments in computational materials physics, accurate prediction of lattice thermal conductivity of solids, especially those with complex structures and/or compositions, remains a challenge. In this talk, I will first present a general overview of several commonly adopted atom-scale simulation techniques and compare the strengths and limitations of these techniques. Then, I will discuss two recent implementations based on the statistical linear response theory and kinetic Peierls-Boltzmann theory by my group. We have adopted these techniques to study (1) the origin of glass-like low thermal conductivity in open-framework thermoelectric materials, and (2) the pressure dependence of lattice thermal conductivity of Earth's lower mantle minerals at extreme pressure and temperature conditions.

February 18, 2011
HiPSEC meeting regarding the transportation of hazardous material and policies for activities within UNLV Labs. In particular, all members should read, understand, and acknowledge receipt of the:
Ruby Fluorimeter Facility Ruby Fluorimeter Facility

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