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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

M06-SX screened-exchange density functional for chemistry and solid-state physics

Significance Density functionals with Hartree–Fock exchange have been widely used for a wide range of chemical applications, but the nonlocal character of exchange makes long-range exchange computationally expensive for solid-state calculations with periodic boundary conditions, and full exchange is nonphysical for condensed-phase systems. Here, we present a screened-exchange (SX) density functional, M06-SX, that is especially designed to have good accuracy for both solid-state physics and chemical applications with less computational cost than full Hartree–Fock exchange. The M06-SX functional gives accuracy comparable to functionals with full Hartree–Fock exchange for predicting chemical properties of molecules, while also being practical with good accuracy for plane wave calculations on band gaps and lattice constants of solids.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Revised M06-L functional for improved accuracy on chemical reaction barrier heights, noncovalent interactions, and solid-state physics

Significance Local exchange−correlation functionals, which depend on the local spin densities, their gradients, and the local spin-specific kinetic energy densities, have been widely used for electronic structure calculations in both chemistry and physics, owing to their computational efficiency in plane wave codes and for large molecules and to their relatively high accuracy for transition metals and other inherently multiconfigurational systems. Minnesota 2006 local functional (M06-L) has proven to be one of the most accurate local functionals currently available, but it has room for improvement with regard to numerical stability and overall accuracy. Here we present a revised M06-L functional, named revM06-L, which gives both smoother potential energy curves and improved overall accuracy, especially for chemical reaction barrier heights, noncovalent interactions, and solid-state physics.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Advances in terahertz solid-state physics and devices

Terahertz (THz) science and technology have attracted tremendous attention owing to their potential applications in areas including high-speed communications, nondestructive evaluation, biological and medical sensing, and national security.1,2 Terahertz waves bridge electronics and photonics, as well as classical and quantum physics, making them equally attractive for fundamental studies of novel physical phenomena. To realize a broad range of real terahertz applications, it is essential to develop compact solid- state devices for terahertz sources, detectors, modulators, and compact systems. These devices often employ quantum materials and heterostructures and can incorporate other features including carrier transfer using atomic layer epitaxy, micro- and electromechanical systems, plasmonic resonators, and metamaterials. To optimize these devices, we have to understand and control ultrafast carrier dynamics in these advanced materials. Furthermore, we have organized a Special Topic in the Journal of Applied Physics to highlight the state-of-the-art in terahertz solid-state devices while also unveiling the properties of these materials on an ultrafast timescale.

47 OTHER INSTRUMENTATION↗
DOE OSTI2016

A Bloch decomposition-based stochastic Galerkin method for quantum dynamics with a random external potential

In this paper, we consider the numerical solution of the one-dimensional Schrödinger equation with a periodic lattice potential and a random external potential. This is an important model in solid state physics where the randomness results from complicated phenomena that are not exactly known. Here we generalize the Bloch decomposition-based time-splitting pseudospectral method to the stochastic setting using the generalized polynomial chaos with a Galerkin procedure so that the main effects of dispersion and periodic potential are still computed together. We prove that our method is unconditionally stable and numerical examples show that it has other nice properties and is more efficient than the traditional method. Finally, we give some numerical evidence for the well-known phenomenon of Anderson localization.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

The Center for Applied Physics and Superconducting Technologies (CAPST)

The Department of Energy’s Fermi National Accelerator Laboratory and Northwestern University have established a new collaboration that enhances both institutions’ scientific research portfolios. The Center for Applied Physics and Superconducting Technologies (CAPST) focuses on the science and applications of superconductivity, with expected advances in the fields of particle physics, solid-state physics, materials science, medicine, energy and environmental sciences. CAPST formally recognizes a broad intersection of scientific pursuits and complementary state-of-the-art facilities. The center lays the groundwork for the cross-utilization of technical expertise, facilities, and equipment and establishes a partnership that will foster joint scientific research, mentorship, and new opportunities for researchers, graduate students, and postdoctoral fellows.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Nuclear resonance scattering of synchrotron radiation as a unique electronic, structural and thermodynamic probe

Discovery of Moessbauer effect in a nuclear transition was a remarkable development. It revealed how long-lived nuclear states with relatively low energies in the kiloelectron volt (keV) region can be excited without recoil. This new effect had a unique feature involving a coupling between nuclear physics and solid-state physics, both in terms of physics and sociology. Physics coupling originates from the fact that recoilless emission and absorption or resonance is only possible if the requirement that nuclei have to be bound in a lattice with quantized vibrational states is fulfilled, and that the finite electron density on the nucleus couples to nuclear degrees of freedom leading to hyperfine interactions. thus, Moessbauer spectroscopy allows peering into solid-state effects using unique nuclear transitions. Sociological aspects of this coupling had been equally startling and fruitful. The interaction between diverse scientific communities, who learned to use Moessbauer spectroscopy proved to be very valuable. For example, biologists, geologists, chemists, physics, materials scientists, and archeologists, all sharing a common spectroscopic technique, also learned to appreciate the beauty and intricacies of each other's fields. As a laboratory-based technique, Moessbauer spectroscopy matured by the end of the 1970s. Further exciting developments took place when accelerator-based techniques were employed, like synchrotron radiation or 'in-beam'Moessbauer experiments with implanted radioactive ions. More recently, two Moessbauer spectrometers on the surface of the Mars kept the technique vibrant and viable up until present time. In this chapter, the authors look into some of the unique aspects of nuclear resonance excited with synchrotron radiation as a probe of condensed matter, including magnetism, valence, vibrations, and lattice dynamics, and review the development of nuclear resonance inelastic x-ray scattering (NRIXS) and synchrotron Moessbauer spectroscopy (SMS). However, to place these two techniques into some perspective with respect to other methods that yield related information, they display their version of a frequently used map of momentum and energy transfer diagram in figure 17.1. Here, various probes like electrons, neutrons, or light, i.e., Brillouin or Raman, and relatively newer forms of X-ray scattering are placed according to their range of energy and momentum transfer taking place during the measurements. Accordingly, NRIXS is a method that needs to be considered as a complementary probe to inelastic neutron and X-ray scattering, while SMS occupies a unique space due to its sensitivity to magnetism, structural deformations, valence, and spin states.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2019

The Superconductor-Superinsulator Transition: S-duality and the QCD on the Desktop

We show that the nature of quantum phases around the superconductor-insulator transition (SIT) is controlled by charge-vortex topological interactions, and does not depend on the details of material parameters and disorder. We find three distinct phases, superconductor, superinsulator, and bosonic topological insulator. The superinsulator is a state of matter with infinite resistance in a finite temperature range, which is the S-dual of the superconductor and in which charge transport is prevented by electric strings binding charges of opposite sign. The electric strings ensuring linear confinement of charges are generated by instantons and are dual to superconducting Abrikosov vortices. Material parameters and disorder enter the London penetration depth of the superconductor, the string tension of the superinsulator and the quantum fluctuation parameter driving the transition between them. They are entirely encoded in four phenomenological parameters of a topological gauge theory of the SIT. Finally, we point out that, in the context of strong coupling gauge theories, the many-body localization phenomenon that is often referred to as an underlying mechanism for superinsulation is a mere transcription of the well-known phenomenon of confinement into solid-state physics language and is entirely driven by endogenous disorder embodied by instantons with no need of exogenous disorder.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Gaps labeling theorem for the bubble-diamond self-similar graphs

Abstract Motivated by the appearance of fractals in several areas of physics, especially in solid state physics and the physics of aperiodic order, and in other sciences, including the quantum information theory, we present a detailed spectral analysis for a new class of fractal-type diamond graphs, referred to as bubble-diamond graphs, and provide a gap-labeling theorem in the sense of Bellissard for the corresponding probabilistic graph Laplacians using the technique of spectral decimation. Labeling the gaps in the Cantor set by the normalized eigenvalue counting function, also known as the integrated density of states, we describe the gap labels as orbits of a second dynamical system that reflects the branching parameter of the bubble construction and the decimation structure. The spectrum of the natural Laplacian on limit graphs is shown generically to be pure point supported on a Cantor set, though one particular graph has a mixture of pure point and singularly continuous components.

Physics↗
DOE OSTI2018

Solving many-body Schrödinger equations with kinetic energy partition method

We present a general formulation of our previously developed kinetic energy partition (KEP) method for solving many-bodySchrödinger equations. In atomic physics, as well as in general molecular and solid state physics, solving many-electronSchrödinger equations is a very challenging task, often called Dirac’s challenge. The central problem is how to properly handle the electron–electron Coulomb repulsion interactions. Using the KEP solution scheme, in addition to dividing the kinetic energy into partial terms, the electron–electron Coulomb interaction is also separated into parts to be associated with a “negative mass” kinetic energy term. Therefore, the full Hamiltonian can be expressed as a simple sum of subsystem Hamiltonians, each representing an effective one-body problem. Using a Hartree-like product in constructing the wave-function, we achieve fast convergence in the calculations of the ground state energies. First, the model Moshinsky atoms are used to illustrate the solution procedure. We then apply this new KEP method to harmonium atoms and obtain precise energies with an error less than 5% using only two basis functions from each subsystem. It is thus very promising that this methodology, when further extended, can be useful for general many-body systems.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Lattice Anharmonicity and Thermal Conductivity from Compressive Sensing of First-Principles Calculations

First-principles prediction of lattice thermal conductivity K L of strongly anharmonic crystals is a long-standing challenge in solid state physics. Using recent advances in information science, we propose a systematic and rigorous approach to this problem, compressive sensing lattice dynamics (CSLD). Compressive sensing is used to select the physically important terms in the lattice dynamics model and determine their values in one shot. Non-intuitively, high accuracy is achieved when the model is trained on first-principles forces in quasi-random atomic configurations. The method is demonstrated for Si, NaCl, and Cu 12 Sb 4 S 13 , an earth-abundant thermoelectric with strong phononphonon interactions that limit the room-temperature K L to values near the amorphous limit.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Zeros of Riemann’s Zeta Functions in the Line z=1/2+it{sub 0}

It was found that, in addition to trivial zeros in points (z = − 2N, N = 1, 2…, natural numbers), the Riemann’s zeta function ζ(z) has zeros only on the line {z=(1/2)+it_0, t_0 is real}. All zeros are numerated, and for each number, N, the positions of the non-overlap intervals with one zero inside are found. The simple equation for the determination of centers of intervals is obtained. The analytical function η(z), leading to the possibility fix the zeros of the zeta function ζ(z), was estimated. To perform the analysis, the well-known phenomenon, phase-slip events, is used. This phenomenon is the key ingredient for the investigation of dynamical processes in solid-state physics, for example, if we are trying to solve the TDGLE (time-dependent Ginzburg-Landau equation).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2016

Perspective: Fundamental aspects of time-dependent density functional theory

In the thirty-two years since the birth of the foundational theorems, time-dependent density functional theory has had a tremendous impact on calculations of electronic spectra and dynamics in chemistry, biology, solid-state physics, and materials science. Alongside the wide-ranging applications, there has been much progress in understanding fundamental aspects of the functionals and the theory itself. This Perspective looks back to some of these developments, reports on some recent progress and current challenges for functionals, and speculates on future directions to improve the accuracy of approximations used in this relatively young theory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Extended temperature-accelerated dynamics: Enabling long-time full-scale modeling of large rare-event systems

A new method, the Extended Temperature-Accelerated Dynamics (XTAD), is introduced for modeling long-timescale evolution of large rare-event systems. The method is based on the Temperature-Accelerated Dynamics approach [M. Sørensen and A. Voter, J. Chem. Phys. 112, 9599 (2000)], but uses full-scale parallel molecular dynamics simulations to probe a potential energy surface of an entire system, combined with the adaptive on-the-fly system decomposition for analyzing the energetics of rare events. The method removes limitations on a feasible system size and enables to handle simultaneous diffusion events, including both large-scale concerted and local transitions. Due to the intrinsically parallel algorithm, XTAD not only allows studies of various diffusion mechanisms in solid state physics, but also opens the avenue for atomistic simulations of a range of technologically relevant processes in material science, such as thin film growth on nano- and microstructured surfaces.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Multiple parameter dynamic photoresponse microscopy for data-intensive optoelectronic measurements of van der Waals heterostructures

Quantum devices made from van der Waals (vdW) heterostructures of two dimensional (2D) materials may herald a new frontier in designer materials that exhibit novel electronic properties and unusual electronic phases. However, due to the complexity of layered atomic structures and the physics that emerges, experimental realization of devices with tailored physical properties will require comprehensive measurements across a large domain of material and device parameters. Such multi-parameter measurements require new strategies that combine data-intensive techniques—often applied in astronomy and high energy physics—with the experimental tools of solid state physics and materials science. We discuss the challenges of comprehensive experimental science and present a technique, called Multi-Parameter Dynamic Photoresponse Microscopy (MPDPM), which utilizes ultrafast lasers, diffraction limited scanning beam optics, and hardware automation to characterize the photoresponse of 2D heterostructures in a time efficient manner. Using comprehensive methods on vdW heterostructures results in large and complicated data sets; in the case of MPDPM, we measure a large set of images requiring advanced image analysis to extract the underlying physics. We discuss how to approach such data sets in general and in the specific case of a graphene–boron nitride–graphite heterostructure photocell.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Summary of Current LLNL Projects with the Russian Federation

Developing a sophisticated theory to understand the electronic structure of 5f-metals is a great challenge to solid state physics. Complicated electronic structures of 5f-metals make their properties strongly sensitive to small energy changes produced by the addition of a small amount of alloy, impurities, or crystal structure defects caused by irradiation. A theoretical material science technique applicable to investigate these effects is atomistic simulation using Classical Molecular Dynamics (CMD). In contrast to ab initio techniques, CMD may include several million particles, so that there is a possibility of direct simulation of very low concentration impurities and defects (as well as phenomena such as plasticity and polymorphous transitions) under given conditions. The goal is to develop theoretical models to understand and predict changes in materials properties of actinides caused by self-irradiation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2016

High-resolution three-dimensional spin- and angle-resolved photoelectron spectrometer using vacuum ultraviolet laser light

We describe a spin- and angle-resolved photoelectron spectroscopy (SARPES) apparatus with a vacuum-ultraviolet (VUV) laser (hν = 6.994 eV) developed at the Laser and Synchrotron Research Center at the Institute for Solid State Physics, The University of Tokyo. The spectrometer consists of a hemispherical photoelectron analyzer equipped with an electron deflector function and twin very-low-energy-electron-diffraction-type spin detectors, which allows us to analyze the spin vector of a photoelectron three-dimensionally with both high energy and angular resolutions. The combination of the high-performance spectrometer and the high-photon-flux VUV laser can achieve an energy resolution of 1.7 meV for SARPES. We demonstrate that the present laser-SARPES machine realizes a quick SARPES on the spin-split band structure of a Bi(111) film even with 7 meV energy and 0.7{sup ∘} angular resolutions along the entrance-slit direction. This laser-SARPES machine is applicable to the investigation of spin-dependent electronic states on an energy scale of a few meV.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Highly ordered graphite (HOPG) to hexagonal diamond (lonsdaleite) phase transition observed on picosecond time scales using ultrafast x-ray diffraction

Here, the response of rapidly compressed highly oriented pyrolytic graphite (HOPG) normal to its basal plane was investigated at a pressure of ~80 GPa. Ultrafast x-ray diffraction using ~100 fs pulses at the Materials Under Extreme Conditions sector of the Linac Coherent Light Source was used to probe the changes in crystal structure resulting from picosecond timescale compression at laser drive energies ranging from 2.5 to 250 mJ. A phase transformation from HOPG to a highly textured hexagonal diamond structure is observed at the highest energy, followed by relaxation to a still highly oriented, but distorted graphite structure following release. We observe the formation of a highly oriented lonsdaleite within 20 ps, subsequent to compression. This suggests that a diffusionless martensitic mechanism may play a fundamental role in phase transition, as speculated in an early work on this system, and more recent static studies of diamonds formed in impact events.

58 GEOSCIENCES↗