Topic
Wigner effect
About: Wigner effect is a research topic. Over the lifetime, 108 publications have been published within this topic receiving 2541 citations. The topic is also known as: Wigner's release & discomposition effect.
Papers published on a yearly basis
Papers
TL;DR: A prominent barrier-state to energy release is identified, a surprising ability of vacancy defects to bridge the widely spaced atomic layers is revealed, and physical property and microstructure changes during irradiation, including interactions with dislocations are discussed.
Abstract: We present findings on the structure, energies and behaviour of defects in irradiated graphitic carbon materials. Defect production due to high-energy nuclear radiations experienced in graphite moderators is generally associated with undesirable changes in internal energy, microstructure and physical properties—the so-called Wigner effect. On the flip side, the controlled introduction and ability to handle such defects in the electron beam is considered a desirable way to engineer the properties of carbon nanostructures. In both cases, the atomic-level details of structure and interaction are only just beginning to be understood. Here, using a model system of crystalline graphite, we show from first-principles calculations, new details in the behaviour of vacancy and interstitial defects. We identify a prominent barrier-state to energy release, reveal a surprising ability of vacancy defects to bridge the widely spaced atomic layers, and discuss physical property and microstructure changes during irradiation, including interactions with dislocations.
391 citations
TL;DR: Direct observation of individual defects during formation and annihilation in the interlayer gap of double-wall carbon nanotubes (DWNT) is demonstrated by high-resolution transmission electron microscopy and finds a threshold for the defect annihilation at 450-500 K, which corresponds to the known temperature for the Wigner energy release.
Abstract: Direct observation of individual defects during formation and annihilation in the interlayer gap of double-wall carbon nanotubes (DWNT) is demonstrated by high-resolution transmission electron microscopy. The interlayer defects that bridge two adjacent graphen layers in DWNT are stable for a macroscopic time at the temperature below 450 K. These defects are assigned to a cluster of one or two interstitial-vacancy pairs ($I\mathrm{\text{\ensuremath{-}}}V$ pairs) and often disappear just after their formation at higher temperatures due to an instantaneous recombination of the interstitial atom with vacancy. Systematic observations performed at the elevated temperatures find a threshold for the defect annihilation at 450--500 K, which, indeed, corresponds to the known temperature for the Wigner energy release.
151 citations
TL;DR: In this article, a method is developed to extract the Wigner term from experimental data. But it cannot be solely explained in terms of correlations between the neutron-proton J=1, T=0 (deuteron-like) pairs.
Abstract: Surfaces of experimental masses of even-even and odd-odd nuclei exhibit a sharp slope discontinuity at N=Z. This cusp (Wigner energy), reflecting an additional binding in nuclei with neutrons and protons occupying the same shell model orbitals, is usually attributed to neutron-proton pairing correlations. A method is developed to extract the Wigner term from experimental data. Both empirical arguments and shell-model calculations suggest that the Wigner term can be traced back to the isospin T=0 part of nuclear interaction. Our calculations reveal the rather complex mechanism responsible for the nuclear binding around the N=Z line. In particular, we find that the Wigner term cannot be solely explained in terms of correlations between the neutron-proton J=1, T=0 (deuteron-like) pairs.
79 citations
TL;DR: In this article, molybdenum and tungsten have been irradiated with pile neutrons at 30°C and at −196°C, respectively, and the recovery of the increase in resistivity has been studied.
72 citations
TL;DR: It is concluded that annihilation of intimate Frenkel defects marks the onset of recovery in electrical resistivity, which occurs when the temperature exceeds about 160 K.
Abstract: Models for radiation damage in graphite are reviewed and compared, leading to a re-examination of the contribution made by vacancies to annealing processes. A method based on density functional theory, using large supercells with orthorhombic and hexagonal symmetry, is employed to calculate the properties and behaviour of lattice vacancies and displacement defects. It is concluded that annihilation of intimate Frenkel defects marks the onset of recovery in electrical resistivity, which occurs when the temperature exceeds about 160 K. The migration of isolated monovacancies is estimated to have an activation energy of E(a) ≈ 1.1 eV. Coalescence into divacancy defects occurs in several stages, with different barriers at each stage, depending on the path. The formation of pairs ultimately yields up to 8.9 eV energy, which is nearly 1.0 eV more than the formation energy for an isolated monovacancy. Processes resulting in vacancy coalescence and annihilation appear to be responsible for the main Wigner energy release peak in radiation-damaged graphite, occurring at about 475 K.
63 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2022 | 1 |
| 2021 | 5 |
| 2020 | 3 |
| 2019 | 3 |
| 2018 | 2 |
| 2017 | 4 |