A5032149414- Ion-surface interactions and analysis
- Laser-induced spectroscopy and plasma
- Advanced Chemical Physics Studies
- Graphene research and applications
- Spectroscopy and Quantum Chemical Studies
- Electron and X-Ray Spectroscopy Techniques
- Machine Learning in Materials Science
- Atomic and Molecular Physics
- High-pressure geophysics and materials
- Cold Atom Physics and Bose-Einstein Condensates
- X-ray Spectroscopy and Fluorescence Analysis
- Laser-Matter Interactions and Applications
- Plasma Diagnostics and Applications
- Laser-Plasma Interactions and Diagnostics
- Optimization and Packing Problems
- Nuclear Physics and Applications
- Quantum Computing Algorithms and Architecture
- Medical Imaging Techniques and Applications
- Geophysical Methods and Applications
- Diamond and Carbon-based Materials Research
- Semiconductor Quantum Structures and Devices
- Optimization and Search Problems
- Scheduling and Optimization Algorithms
- X-ray Diffraction in Crystallography
- Spectroscopy and Laser Applications
Sandia National Laboratories
2022-2025
Sandia National Laboratories California
2022-2023
University of Illinois Urbana-Champaign
2019-2021
Sobolev Institute of Mathematics
2001-2019
Sorbonne Université
2018
Université Paris Cité
2018
Odesa I. I. Mechnikov National University
1994-1996
P.N. Lebedev Physical Institute of the Russian Academy of Sciences
1980
We report the results of second charged-particle transport coefficient code comparison workshop, which was held in Livermore, California on 24–27 July 2023. This workshop gathered theoretical, computational, and experimental scientists to assess state computational techniques for understanding coefficients relevant high-energy-density plasma science. Data electronic ionic coefficients, namely, direct current electrical conductivity, electron thermal ion shear viscosity, conductivity were...
Stopping power is the rate at which a material absorbs kinetic energy of charged particle passing through it—one many properties needed over wide range thermodynamic conditions in modeling inertial fusion implosions. First-principles stopping calculations are classically challenging because they involve dynamics large electronic systems far from equilibrium, with accuracies that particularly difficult to constrain and assess warm-dense preceding ignition. Here, we describe protocol for using...
Linear-response time-dependent density-functional theory (TDDFT) can describe excitonic features in the optical spectra of insulators and semiconductors, using exchange-correlation (xc) kernels behaving as $\ensuremath{-}1/{k}^{2}$ to leading order. We show how excitons be modeled real-time TDDFT, an xc vector potential constructed from approximate, long-range corrected kernels. demonstrate, for various materials, that this approach is consistent with frequency-dependent linear response,...
We use first-principles calculations to uncover and explain a new type of anomalous low-velocity stopping effect in proton-irradiated graphene. attribute shoulder feature that occurs exclusively for channeling protons enhanced electron capture from $\sigma$+$\pi$ orbitals. Our analysis emission indicates backward is more sensitive proton trajectory than forward could thus produce higher contrast images ion microscopy. For slow protons, we observe steep drop emission, consistent with...
Abstract Real-time time-dependent density functional theory (TDDFT) is presently the most accurate available method for computing electronic stopping powers from first principles. However, obtaining application-relevant results often involves either costly averages over multiple calculations or ad hoc selection of a representative ion trajectory. We consider broadly applicable, quantitative metric evaluating and optimizing trajectories in this context. This methodology enables rigorous...
Real-time time-dependent density functional theory (TDDFT) is widely considered to be the most accurate available method for calculating electronic stopping powers from first principles, but there have been relatively few assessments of consistency its predictions across different implementations. This problem particularly acute in warm dense regime, where computational costs are high and experimental validation rare resource intensive. We report a comprehensive cross-verification power...
Thomson scattering spectra measure the response of plasma particles to incident radiation. In warm dense matter, which is opaque visible light, x-ray (XRTS) enables a detailed probe electron distribution and has been used as diagnostic for temperature, density, ionization. this work, we examine sensitivities inelastic XRTS signatures modeling details, including dynamic collision frequency electronic density states. Applying verified Monte Carlo inversion methods structure factors obtained...
Simulations and diagnostics of high-energy-density plasmas warm dense matter rely on models material response properties, both static dynamic (frequency-dependent). Here, we systematically investigate variations in electron-ion collision frequencies $\nu(\omega)$ using data from a self-consistent-field average-atom model. We show that including the full quantum density states, strong collisions, inelastic collisions lead to significant changes $\nu(\omega)$. These result red shifts...
Highly energetic ions traversing a two-dimensional material such as graphene produce strong electronic excitations. Electrons excited to energy states above the work function can give rise secondary electron emission, reducing amount of that remains in after ion impact. be either emitted (kinetic transfer) or captured by passing (potential transfer). To elucidate this behavior is absent three-dimensional materials, we simulate dynamics during first femtoseconds We employ two conceptually...
Intimately intertwined atomic and electronic structures of point defects govern diffusion-limited corrosion underpin the operation optoelectronic devices. For some materials, complex energy landscapes containing metastable defect configurations challenge first-principles modeling efforts. Here, we thoroughly reevaluate native geometries for illustrative case ofα-Al2O3by comparing three methods sampling candidate in density functional theory calculations: displacing atoms near a naively...
We present a first-principles study of pre-equilibrium stopping power and projectile charge capture in thin aluminum sheets irradiated by 6--60 keV protons. Our time-dependent density functional theory calculations reveal enhanced compared to bulk aluminum, particularly near the entrance layers. propose additional excitation channel surface plasma oscillations as most plausible explanation for this behavior. also introduce technique compute orbital-resolved state proton after transmission...
Abstract Computational materials modeling and design has emerged as a vital component of materi- als research development in academic, industrial, national lab settings. In response, US Materials Science Engineering (MatSE) departments the federal government rec- ognize need to incorporate computational training into undergraduate MatSE education. Our faculty team at University Illinois Urbana-Champaign (UIUC) is addressing this growing with comprehensive integrated cur- riculum. Throughout...
Abstract The extreme sensitivity of 2D materials to defects and nanostructure requires precise imaging techniques verify presence desirable absence undesirable features in the atomic geometry. Helium-ion beams have emerged as a promising tool, achieving up 20 times higher resolution 10 larger depth-of-field than conventional or environmental scanning electron microscopes. Here, we offer first-principles theoretical insights advance ion-beam atomically thin by performing real-time...
Characteristic properties of secondary electrons emitted from irradiated two-dimensional materials arise multi-length and multi-time-scale relaxation processes that connect the initial nonequilibrium excited electron distribution with their eventual emission. To understand these processes, which are critical for using as high-resolution thermalization probes, we combine first-principles real-time dynamics irradiation experiments. Our data cold hot proton-irradiated graphene show signatures...
Thomson scattering spectra measure the response of plasma particles to incident radiation. In warm dense matter, which is opaque visible light, x-ray (XRTS) enables a detailed probe electron distribution and has been used as diagnostic for temperature, density, ionization. this work, we examine sensitivities inelastic XRTS signatures modeling details including dynamic collision frequency electronic density states. Applying verified Monte Carlo inversion methods structure factors obtained...
Bound-bound transitions can occur when localized atomic orbitals are thermally depleted, allowing excitations that would otherwise be forbidden at zero temperature. We predict signatures of bound-bound in x-ray Thomson scattering measurements laboratory-accessible warm dense conditions. Efficient average-atom models amended to include quasibound states achieve continuity observables under ionization and agree with time-dependent density functional theory their prediction these signatures,...
Real-time time-dependent density functional theory (TDDFT) is widely considered to be the most accurate available method for calculating electronic stopping powers from first principles, but there have been relatively few assessments of consistency its predictions across different implementations. This problem particularly acute in warm dense regime, where computational costs are high and experimental validation rare resource intensive. We report a comprehensive cross-verification power...
The nascent but rapidly growing field of Quantum Information Science and Technology has led to an increased demand for skilled quantum workers opportunity build a diverse workforce at the outset. In order meet this encourage women underrepresented minorities in STEM consider career QIST, we have developed curriculum introducing computing teachers students high school level with no prerequisites. 2022, was delivered over course two one-week summer camps, one targeting another students. Here,...