A5015314108- High-pressure geophysics and materials
- Advanced Chemical Physics Studies
- Semiconductor materials and devices
- Energetic Materials and Combustion
- Surface and Thin Film Phenomena
- Astro and Planetary Science
- Metal and Thin Film Mechanics
- Rare-earth and actinide compounds
- Nuclear Materials and Properties
- Silicon Nanostructures and Photoluminescence
- Orthopedic Infections and Treatments
- Advanced Thermodynamics and Statistical Mechanics
- Total Knee Arthroplasty Outcomes
- Phase Equilibria and Thermodynamics
- Diamond and Carbon-based Materials Research
- nanoparticles nucleation surface interactions
- Orthopaedic implants and arthroplasty
- Geological and Geochemical Analysis
- Crystallography and molecular interactions
- Nuclear Physics and Applications
- Advanced Materials Characterization Techniques
- Medical Imaging Techniques and Applications
- Carbon Nanotubes in Composites
- Free Radicals and Antioxidants
- Planetary Science and Exploration
Lawrence Livermore National Laboratory
2006-2025
University of California, Los Angeles
1991-2025
Duke University Hospital
2024-2025
Duke Medical Center
2022
Beijing University of Posts and Telecommunications
2012
UCLA Health
1992
Executive Office of the President
1990
University of California Office of the President
1990
At the 26th AIRAPT conference in 2017, a task group was formed to work on an International Practical Pressure Scale (IPPS). This report summarizes activities of toward IPPS ruby gauge. We have selected three different approaches establishing relation between pressure (P) and R1-line shift (Δλ) with groups optimal reference materials for applying these approaches. Using polynomial form second order, recommended gauge (referred as Ruby2020) is expressed by:...
The mechanism of the gas phase unimolecular decomposition hexahydro-1,3,5,-trinitro-1,3,5,-triazine (RDX) has been investigated using first principles gradient-corrected density functional theory. We have calculated potential energy profile for two previously suggested dissociation channels: (I) N−NO2 bond rupture, and (II) concerted ring fission to three methylenenitramine molecules. activation barriers channels I II are predicted be 34.2 52.5 kcal/mol at B-PW91/cc-pVDZ level,...
We present a realistic simulation of the reaction fluorine with Si(100). Isothermal molecular dynamics simulations, using an analytic many-body potential fit to first-principles quantum mechanical adsorbate-surface and experimental gas phase data, show initial buildup fluorosilyl layer necessary for etching. Several aspects microscopic mechanism are revealed. These simulations represent first time that first-principles-derived surface have been carried out; we this approach is critical...
We describe the construction of a wide-ranged multiphase equation state for elemental iron, consisting four solid phases and one fluid phase. The free-energy models are constrained by fitting to broad swath ambient, static, dynamic high-pressure experimental data, including recent ramp-compression shock--ramp recrystallization experiments. In order better conditions near Earth's inner-core boundary, ab initio electronic-structure calculations various types have been carried out hcp liquid...
Abstract The need for nonaddictive and effective treatments chronic pain are at an all-time high. Historical precedence, now clinical evidence, supports the use of cannabis alleviating pain. A plethora research on delta-9-tetrahydrocannabinol exists, yet is comprised a multitude constituents, some which possess analgesic potential, that have not been systematically investigated, including terpene myrcene. Myrcene attenuates hypersensitivity in preclinical models one most abundant terpenes...
Nuclear materials often evolve into two-phase systems comprising a bulk matrix with dispersed inert-gas bubbles. The presence of these bubbles can have consequences to the thermomechanical response and is key life-limiting factor in some nuclear fuel forms. Understanding behavior two-phase, bubble-matrix is, thus, important improved predictive models frameworks for many applications. While temperature excursions been characterized, fewer studies focused on evolution under pressure. In this...
Shock temperatures of pentaerythritol tetranitrate (PETN) single crystals have been measured by using a nanosecond time-resolved spectropyrometric system operated at six discrete wavelengths between 350 and 700 nm. The results show that the shock sensitivity PETN is strongly dependent on crystal orientation: Sensitive along propagation normal to (110) plane, but highly insensitive (100) plane. detonation temperature is, however, independent from orientation determined be 4140 (±70) K. data...
Using gradient-corrected density functional theory, we have investigated various competing mechanisms involved in the early stages of decomposition a "push−pull" (containing both electron-donating and -withdrawing groups) aromatic (1,3,5-triamino-2,4,6-trinitrobeznene, TATB), particularly how hydrogen transfer affects competition between ring closure single bond scission. On basis obtained energetics, found several previously suggested to be energetically disfavored. These include direct...
We report first-principles electronic-structure calculations related to the initial fluorination of Si(100)-2\ifmmode\times\else\texttimes\fi{}1 surface. Embedded finite silicon clusters are used model an extended Two theoretical approaches, including a geometry-mapping procedure and evaluation lateral interactions via dicluster model, presented. Adsorption up 2.0 monolayers fluorine is considered. Heats adsorption, activation barriers, preferred binding sites, equilibrium geometries, charge...
It has been recently suggested that elemental carbon may be a promising candidate to exhibit liquid-liquid phase transition (LLPT). We report the results of first-principles molecular dynamics simulations showing no evidence LLPT in carbon, same temperature and pressure range where such was found using empirical calculations. Our indicate continuous evolution from primarily $sp$-bonded liquid an $s{p}^{2}$-like $s{p}^{3}$-like fluid, as function pressure, above graphite melting line. The...
The electronic structure of the energetic crystalline solid TATB (1,3,5-triamino-2,4,6-trinitrobenzene) has been studied as a function uniaxial compression, in order to examine insulator-to-metal transition. Both ab initio density-functional theory and configuration interaction methods have used determine band gaps. Band-gap closure is found begin near 47% strain. A lower bound for metallization pressure predicted at 120 GPa, far above detonation TATB. Therefore, we conclude that excitation...
The authors use intense laser pulses to compress solid tantalum pressures in excess of 20 million atmospheres. By combing their experimental measurements with existing high-pressure, high-temperature data on Ta, they can create an experimentally bounded equation state that is valid up multiterapascal and thousands degrees kelvin. may serve as a useful pressure standard at the extreme compressions elevated temperatures now achievable state-of-the-art static compression experiments. This work...
We describe the construction of a three-phase equation state for elemental beryllium. The phases considered are: ambient hcp phase, high-temperature bcc and liquid. free energies solid are constructed from cold, ion-thermal, electron-thermal components derived ab initio electronic structure-based calculations. find that phase is unstable near conditions even at high pressures which stable, bcc-hcp energy barrier can be as small few hundred kelvins. liquid based on model Chisolm Wallace...
We construct a family of beryllium (Be) multiphase equation state (EOS) models that consists baseline ("optimal") EOS and variations on the to account for physics-based uncertainties. The Be is constructed reproduce set self-consistent data theory including known phase boundaries, principal Hugoniot, isobars, isotherms from diamond-anvil cell experiments. Three phases are considered, hexagonal closed-packed (hcp) phase, liquid, theoretically predicted high-pressure body-centered cubic (bcc)...
We present the results of first-principles-derived Monte Carlo simulations H adatom diffusion on Si(100)-2\ifmmode\times\else\texttimes\fi{}1 surface. developed an analytical Si/H potential which was fit to first-principles electronic-structure calculations adsorption and embedded silicon clusters designed model Si(100)-2\ifmmode\times\else\texttimes\fi{}1. With this interaction potential, we calculated rate constants for a hopping from one site another, both parallel perpendicular dimer...
This paper presents first-principles total-energy calculations of hydrogen-adatom diffusion on a Si(100)-2\ifmmode\times\else\texttimes\fi{}1 reconstructed surface. The transition states for hydrogen-atom-diffusion pathways were established by mapping out the potential energy hydrogen atom jumping between dangling bonds surface modeled embedded finite silicon clusters. barriers are high (2--3 eV) and wide (\ensuremath{\sim}3--4 \AA{}), suggesting that H-atom Si(100) proceeds via mostly...
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTMechanistic predictions for fluorine etching of silicon(100)Christine J. Wu and Emily A. CarterCite this: Am. Chem. Soc. 1991, 113, 24, 9061–9062Publication Date (Print):November 1, 1991Publication History Published online1 May 2002Published inissue 1 November 1991https://doi.org/10.1021/ja00024a005RIGHTS & PERMISSIONSArticle Views187Altmetric-Citations42LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum full text article...
Sophisticated hydrodynamic codes are commonly used to understand and predict events relevant natural applied sciences. The degree which these simulations reflect reality, however, is dependent on how well we the materials underlying physics involved. These research communities need material models that communicate uncertainty in physical properties, at their basest form comes from experimental measurements. We have constructed a new framework for using both measurements associated...
Large laser facilities have recently enabled material characterization at the pressures of Earth and Super-Earth cores. However, temperature compressed materials has been largely unknown, or solely relied on models simulations, due to lack diagnostics under these challenging conditions. Here, we report temperature, density, pressure, local structure copper determined from extended x-ray absorption fine velocimetry up 1 Terapascal. These results nearly double highest pressure which reported...