skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study

Abstract

Understanding radiation-induced defect formation in carbon materials is crucial for nuclear technology and for the manufacturing of nanostructures with desired properties. Using first-principles molecular dynamics, we perform a systematic study of the nonequilibrium processes of radiation damage in graphite. Our study reveals a rich variety of defect structures (vacancies, interstitials, intimate interstitial-vacancy pairs, and in-plane topological defects) with formation energies of 5-15 eV. We clarify the mechanisms underlying their creation and find unexpected preferences for particular structures. Possibilities of controlled defect-assisted engineering of nanostructures are analyzed. In particular, we conclude that the selective creation of two distinct low-energy intimate Frenkel pair defects can be achieved by using a 90-110 keV electron beam irradiation.

Authors:
; ; ;  [1]
  1. Ecole Polytechnique Federale de Lausanne (EPFL), Institute of Chemical Sciences and Engineering, CH-1015 Lausanne (Switzerland)
Publication Date:
OSTI Identifier:
20957782
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. B, Condensed Matter and Materials Physics; Journal Volume: 75; Journal Issue: 11; Other Information: DOI: 10.1103/PhysRevB.75.115418; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; ELECTRON BEAMS; EV RANGE; FORMATION HEAT; FRENKEL DEFECTS; GRAPHITE; INTERSTITIALS; IRRADIATION; KEV RANGE; MOLECULAR DYNAMICS METHOD; NANOSTRUCTURES; PHYSICAL RADIATION EFFECTS

Citation Formats

Yazyev, Oleg V., Tavernelli, Ivano, Rothlisberger, Ursula, and Helm, Lothar. Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study. United States: N. p., 2007. Web. doi:10.1103/PHYSREVB.75.115418.
Yazyev, Oleg V., Tavernelli, Ivano, Rothlisberger, Ursula, & Helm, Lothar. Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study. United States. doi:10.1103/PHYSREVB.75.115418.
Yazyev, Oleg V., Tavernelli, Ivano, Rothlisberger, Ursula, and Helm, Lothar. Thu . "Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study". United States. doi:10.1103/PHYSREVB.75.115418.
@article{osti_20957782,
title = {Early stages of radiation damage in graphite and carbon nanostructures: A first-principles molecular dynamics study},
author = {Yazyev, Oleg V. and Tavernelli, Ivano and Rothlisberger, Ursula and Helm, Lothar},
abstractNote = {Understanding radiation-induced defect formation in carbon materials is crucial for nuclear technology and for the manufacturing of nanostructures with desired properties. Using first-principles molecular dynamics, we perform a systematic study of the nonequilibrium processes of radiation damage in graphite. Our study reveals a rich variety of defect structures (vacancies, interstitials, intimate interstitial-vacancy pairs, and in-plane topological defects) with formation energies of 5-15 eV. We clarify the mechanisms underlying their creation and find unexpected preferences for particular structures. Possibilities of controlled defect-assisted engineering of nanostructures are analyzed. In particular, we conclude that the selective creation of two distinct low-energy intimate Frenkel pair defects can be achieved by using a 90-110 keV electron beam irradiation.},
doi = {10.1103/PHYSREVB.75.115418},
journal = {Physical Review. B, Condensed Matter and Materials Physics},
number = 11,
volume = 75,
place = {United States},
year = {Thu Mar 15 00:00:00 EDT 2007},
month = {Thu Mar 15 00:00:00 EDT 2007}
}
  • A universal-parameter tight-binding molecular-dynamics technique that correctly treats interactions in nontetrahedral as well as multicoordinated covalent systems is used to obtain equilibrium geometries for carbon clusters of arbitrary size. For [ital N][le]10 the ground states are determined to be linear chains for odd [ital N] and closed rings for even [ital N]. The minimum-energy cyclic structures exhibit symmetry-lowering in-plane distortions rather than being regular polygons. These findings are in complete agreement with available [ital ab] [ital initio] results. Large clusters of atoms are used to demonstrate the validity of the method to simulate bulklike diamond and single-layer graphitic structures. Themore » well known 2[times]1 reconstruction for the (001) face is observed for the diamond cluster.« less
  • Nucleation is a fundamental step in crystal growth. Of environmental and materials relevance are reactions that lead to nucleation of iron oxyhydroxides in aqueous solutions. These reactions are difficult to study experimentally due to their rapid kinetics. Here, we used classical molecular dynamics simulations to investigate nucleation of iron hydroxide/oxyhydroxide nanoparticles in aqueous solutions. Results show that in a solution containing ferric ions and hydroxyl groups, iron–hydroxyl molecular clusters form by merging ferric monomers, dimers, and other oligomers, driven by strong affinity of ferric ions to hydroxyls. When deprotonation reactions are not considered in the simulations, these clusters aggregate tomore » form small iron hydroxide nanocrystals with a six-membered ring-like layered structure allomeric to gibbsite. By comparison, in a solution containing iron chloride and sodium hydroxide, the presence of chlorine drives cluster assembly along a different direction to form long molecular chains (rather than rings) composed of Fe–O octahedra linked by edge sharing. Further, in chlorine-free solutions, when deprotonation reactions are considered, the simulations predict ultimate formation of amorphous iron oxyhydroxide nanoparticles with local atomic structure similar to that of ferrihydrite nanoparticles. Overall, our simulation results reveal that nucleation of iron oxyhydroxide nanoparticles proceeds via a cluster aggregation-based nonclassical pathway.« less
    Cited by 12
  • Nucleation is a fundamental step in crystal growth. Of environmental and materials relevance are reactions that lead to nucleation of iron oxyhydroxides in aqueous solutions. These reactions are difficult to study experimentally due to their rapid kinetics. Here, we used classical molecular dynamics simulations to investigate nucleation of iron hydroxide/oxyhydroxide nanoparticles in aqueous solutions. Results show that in a solution containing ferric ions and hydroxyl groups, iron–hydroxyl molecular clusters form by merging ferric monomers, dimers, and other oligomers, driven by strong affinity of ferric ions to hydroxyls. When deprotonation reactions are not considered in the simulations, these clusters aggregate tomore » form small iron hydroxide nanocrystals with a six-membered ring-like layered structure allomeric to gibbsite. By comparison, in a solution containing iron chloride and sodium hydroxide, the presence of chlorine drives cluster assembly along a different direction to form long molecular chains (rather than rings) composed of Fe–O octahedra linked by edge sharing. Further, in chlorine-free solutions, when deprotonation reactions are considered, the simulations predict ultimate formation of amorphous iron oxyhydroxide nanoparticles with local atomic structure similar to that of ferrihydrite nanoparticles. Overall, our simulation results reveal that nucleation of iron oxyhydroxide nanoparticles proceeds via a cluster aggregation-based nonclassical pathway.« less
  • Understanding the nature and formation of the solid–electrolyte interphase (SEI) formed in electrochemical storage devices, such as Li-ion batteries, is most important for improving functionality. Few experiments exist that adequately probe the SEI, particularly in situ. We perform predictive ab initio molecular dynamics simulations of the anode–electrolyte interface for several electrolytes and interface functionalizations. These show strongly differing effects on the reducibility of the electrolyte. Electrolyte reduction occurs rapidly, on a picosecond time scale. Orientational ordering of electrolyte near the interface precedes reduction. The reduced species depend strongly on surface functionalization and presence of LiPF6 salt. While LiPF6 salt inmore » ethylene carbonate is more stable at a hydrogen-terminated anode, oxygen/hydroxyl termination causes spontaneous dissociation to form LiF and other fluorophosphates. LiF migrates to the interface creating chainlike structures, consistent with experimental observations of LiF agglomeration. Inorganic products such as LiF and Li2CO3 migrate closer to the anode than purely organic components, consistent with their more ionic character. Significantly, we conclude that while the electrolyte reduction occurs at the molecular level near the interface, requiring specific alignments and proximity, the reducibility is governed by the average reduction potential barrier between the electrode (anode) and the electrolyte.« less