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Enthalpy Landscape Dictates the Irradiation-Induced Disordering of Quartz

N. M. Anoop Krishnan, Bu Wang, Yingtian Yu, Yann Le Pape, Gaurav Sant, and Mathieu Bauchy
Phys. Rev. X 7, 031019 – Published 28 July 2017
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Abstract

Under irradiation, minerals tend to experience an accumulation of structural defects, ultimately leading to a disordered atomic network. Despite the critical importance of understanding and predicting irradiation-induced damage, the physical origin of the initiation and saturation of defects remains poorly understood. Here, based on molecular dynamics simulations of α-quartz, we show that the topography of the enthalpy landscape governs irradiation-induced disordering. Specifically, we show that such disordering differs from that observed upon vitrification in that, prior to saturation, irradiated quartz accesses forbidden regions of the enthalpy landscape, i.e., those that are inaccessible by simply heating and cooling. Furthermore, we demonstrate that damage saturates when the system accesses a local region of the enthalpy landscape corresponding to the configuration of an allowable liquid. At this stage, a sudden decrease in the heights of the energy barriers enhances relaxation, thereby preventing any further accumulation of defects and resulting in a defect-saturated disordered state.

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  • Received 9 January 2017

DOI:https://doi.org/10.1103/PhysRevX.7.031019

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

Published by the American Physical Society

  • The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Physics Subject Headings (PhySH)

  1. Research Areas
  1. Physical Systems
Condensed Matter, Materials & Applied PhysicsPolymers & Soft Matter

Authors & Affiliations

N. M. Anoop Krishnan1, Bu Wang1,2, Yingtian Yu1, Yann Le Pape3, Gaurav Sant2,4, and Mathieu Bauchy1,*

  • 1Laboratory for the Physics of Amorphous and Inorganic Solids (PARISlab), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA
  • 2Laboratory for the Chemistry of Construction Materials (LC2), Department of Civil and Environmental Engineering, University of California, Los Angeles, California 90095, USA
  • 3Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, Tennessee 37831-6148, USA
  • 4California Nanosystems Institute (CNSI), University of California, Los Angeles, California 90095, USA

  • *Corresponding author. bauchy@ucla.edu

Popular Summary

When exposed to radiation, materials can undergo significant damage that ultimately leads to changes in some properties, such as density or stiffness. Understanding the origin of irradiation-induced damage has remained a holy grail in materials science both from a fundamental perspective and for practical applications such as the safety of nuclear power plants, nuclear waste immobilization, and controlled doping of semiconductors. Although several empirical models have been proposed over the last few decades, a physically sound explanation of the origin of structural defects has remained elusive. Based on the enthalpy landscape approach—a technique that maps changes to the total heat content of an object for different temperatures—this paper offers a novel self-consistent understanding of the origin and saturation of irradiated-induced defects.

Using realistic reactive molecular dynamics simulations of irradiation in quartz (an archetypical oxide crystal), we reveal that the roughness of the enthalpy landscape controls the nature and extent of structural damage upon irradiation. Specifically, we show that damage saturates when the material reaches the state of a liquid. At this stage, the height of the energy barriers of the enthalpy landscape drops, which allows the system to explore many configurations upon additional energy deposition. This facilitates relaxation and prevents any further accumulation of defects.

Overall, our study demonstrates that the enthalpy landscape framework can provide a consistent answer to the long-standing question of the nature of irradiation-induced damage.

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Vol. 7, Iss. 3 — July - September 2017

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