DOCSLIB.ORG

Ab Initio Studies of Defect Concentrations and Diffusion In

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Ab Initio Studies of Defect Concentrations and Diffusion In Ab initio studies of defect concentrations and diffusion in metal oxides Kilian Frensch Condensed Matter Theory Group Department of Physics Imperial College London A thesis submitted for the degree of Doctor of Philosophy 2011 \In physics, you don't have to go around making trouble for yourself - nature does it for you." - Frank Anthony Wilczek Declaration of Originality I certify that, except where appropriately referenced, the work is that of the author alone and has not been previously submitted to qualify for any other academic award. - Kilian Frensch, July 2011 Abstract This work presents a methodology for determining the concentrations and diffusion coefficients of point defects in metal oxides using ab initio calculations of defect for- mation energies and diffusion barriers, and the binding energies of defect-impurity clusters. The methodology is applied to analyse the long-standing mysteries sur- rounding the mechanism of self-diffusion in α-Al2O3. Al2O3 is a prototypical large band gap ceramic with extensive applications, many of which depend on its defect chemistry. In particular, point defect concentrations, that vary with temperature and impurity doping, govern diffusion properties such as creep, sintering, or the oxidation rate of Al-containing alloys. Experimental measurements of the self-diffusion coefficients in bulk alumina reveal three important truths that theory cannot reconcile, collectively termed the 'corundum conundrum'. First, large experimental activation energies for oxygen and aluminum diffusion and low theoretical formation energies imply unreasonably high diffusion barriers of ∼ 5eV. Second, aluminum diffusion is orders of magnitude faster than oxygen diffusion. Third, the oxygen diffusion coefficient is relatively insensitive to aliovalent doping, increasing by a factor of 100 on heavy Mg2+-doping, and decreasing by a similar amount on Ti4+-doping. We attempt to resolve this conundrum by calculating the formation energies and binding energies of a raft of native point defects and defect-impurity clusters as func- tions of temperature T and oxygen partial pressure pO2 , and the diffusion barriers of the native defects, using density functional theory. We then use a thermodynamic mass action approach to determine the concentrations of the defects and clusters, and the diffusion coefficients of the defects, as functions of T , pO2 , and the con- centrations of aliovalent dopants, [Mg2+] and [Ti4+]. In the process, we discover new ground-state defect structures for the aluminum vacancy and oxygen intersti- tial, and demonstrate that diffusion of aluminum vacancies and interstitials occurs by extended vacancy and interstitialcy mechanisms, and oxygen interstitials by a dumbbell interstitialcy mechanism, all of which yield much lower migration barriers than previous theory. Unfortunately, the results do not demonstrate the experimentally-found insensitivity of the oxygen diffusivity to aliovalent doping. This could be an artefact of approx- imations within density functional theory and our methodology, and we show that modest changes in the calculated binding energies lead to significant defect cluster- ing. This defect clustering could result in a buffering mechanism that can explain the insensitivity of the diffusivity to aliovalent doping, and may occur in other ionic materials. More accurate calculations, employing hybrid functionals or quantum Monte Carlo methods, may be necessary to elucidate this effect, but are currently computationally intractable for our purposes. 5 Acknowledgements This PhD has undeniably been the most challenging episode of my life this far. It would not have been possible without the immense support I received during the time. Above all, I would like to thank Nick, the most devoted and brilliant young scientist I have met, for his neverending help and advice. Much of this work is due to him. Matthew and Mike have been a fountain of knowledge, motivation, and inspiration, and the best supervisors a student could ask for. Arthur contributed crucial elements to this work at a pivotal stage, and was a driving force during the final year of my work. I would like to thank my friends, in particular Ola and Adam, for putting up with much of the frustration that accompanied the work and making the time all the more fun. I could thank Racheal for any one of a number of things over the past years, but each would only describe a small part of what makes her special. Suffice it to say that she is most definitely `the better half' and has contributed enormously to this thesis. My family has always supported me and I thank them for their guidance and love. My father has been an inspiration to me from a young age, and I dedicate this thesis to him, my mother, and Antonia, who have always been the nucleus of my motivation. Table of Contents 1 Introduction 11 2 The many body problem 15 2.1 Introduction . 15 2.2 The Hamiltonian . 16 2.2.1 The Born-Oppenheimer approximation . 18 2.3 Density Functional Theory . 19 2.3.1 The first Hohenberg-Kohn theorem . 19 2.3.2 The second Hohenberg-Kohn theorem . 20 2.3.3 The Kohn-Sham ansatz . 21 2.3.4 Exchange-correlation functionals . 25 2.3.5 Basis sets . 27 2.3.6 Pseudopotentials . 28 2.4 Quantum Monte Carlo . 30 2.4.1 Variational Monte Carlo . 30 2.4.2 Diffusion Monte Carlo . 32 2.4.3 Trial wave functions . 39 2.4.4 Wave function optimisation . 41 3 Point defects in solids 43 3.1 Introduction . 43 3.2 Defect species and notation . 45 3.3 Defect concentrations in the dilute limit . 47 3.3.1 The law of mass action . 47 3.3.2 Defect concentrations in the canonical ensemble . 48 3.3.3 Intrinsic and extrinsic defects . 54 3.4 Thermodynamics of defect formation energies . 57 3.4.1 Zhang-Northrup formalism . 57 3.4.2 Chemical potentials . 59 3.5 Density functional theory calculations of defect formation energies . 65 3.5.1 Vibrational effects . 65 3.5.2 Band gap corrections . 68 3.5.3 Finite-size effects . 71 7 Table of Contents 3.6 Diffusion kinetics of defects . 78 3.6.1 Mechanisms of diffusion . 79 3.6.2 Activation energies and diffusion barriers . 81 3.6.3 Fick's laws . 83 3.6.4 Diffusion coefficients from random walk diffusion . 86 3.6.5 Correlation effects . 88 3.6.6 Experimental methods . 93 4 Point defects and diffusion in Al2O3 97 4.1 Introduction . 98 4.2 Experimental background . 98 4.2.1 Oxygen diffusion . 99 4.2.2 Oxygen diffusion buffering in doped alumina . 102 4.2.3 Aluminium diffusion . 105 4.2.4 Anisotropy . 107 4.2.5 Alternative species . 108 4.3 Previous theoretical work . 109 4.4 Density functional theory calculations . 115 4.4.1 Geometry and basis set convergence . 115 4.4.2 Defect species and complexes . 122 4.4.3 Defect formation energies and cluster binding energies . 145 4.4.4 Chemical potentials . 152 4.4.5 Band gap corrections . 154 4.4.6 Finite-size scaling . 156 4.4.7 Vibrational contributions . 160 4.4.8 Diffusion barriers . 162 4.5 Defect concentrations . 179 4.6 Diffusion coefficients . 190 4.7 Impurity solubilities . 194 4.8 Quantum Monte Carlo calculations . 198 4.8.1 Trial wave functions . 199 4.8.2 Jastrow optimisation . 200 4.8.3 QMC band gaps . 202 4.8.4 Errors . 203 4.8.5 Diffusion barriers . 206 8 Table of Contents 5 Conclusion 209 A Point defects in solids 213 A.1 Arrhenius relationships of activation energies of diffusion . 213 A.2 Einstein equation from random walk diffusion . 214 A.3 Diffusion coefficients from random walk diffusion . 215 A.4 Correlation factors for native defect diffusion in alumina . 217 9 1 Introduction Physicists, and scientists in general, enjoy classifying things into distinct categories. It is therefore only natural that they classify themselves, creating the great divide in physics, between `experimentalists' and `theorists'. Of course, each group consid- ers itself superior to the other, occasionally even suggesting that the other merely exists to support it. However, physics is impervious to all this. It remains physics, regardless of who studies it in what way. Neither experimentalists nor theorists `invent' physics with their discoveries. In fact, both rely on the other for their own recognition, whether it be a theorist in need of experimental verification of their prediction, or an experimentalist in need of a theoretical explanation of their result. Ultimately, every physicist is actually part both, and if we wish to have a complete understanding of the world around us, experiment and theory must walk hand in hand. This study was motivated by the gap between experiment and theory in the under- standing of point defect diffusion in Al2O3, or alumina. For almost half a century, tracer diffusion studies on alumina doped with aliovalent impurities have shown that the concentrations of the native defects in alumina are strongly buffered. Theory has been unable to explain the cause of this buffering, in part due to the theoretical methods employed. This disparity between theory and experiment has been coined the `corundum conundrum' in a recent paper [80]. The current study attempts to re- solve this conundrum using a full ab initio, meaning from first-principles, approach. The results from this approach suggest that density functional theory calculations employing an LDA functional are unable to rationalise this long-standing conun- drum, and that further work using hybrid functionals or quantum Monte Carlo methods is necessary. Although results are presented for alumina, the theoretical 11 Chapter 1: Introduction formalism underlying the current study is general, and can be applied to a wide range of other metal oxides. In Chapter 2, the theoretical methods used in this study are presented: density functional theory (DFT) and quantum Monte Carlo (QMC).
Load more

Recommended publications
  • Electromigration in Thin Films of Aluminium"
    Co / Y A thesis entitled "ELECTROMIGRATION IN THIN FILMS OF ALUMINIUM" by Stephen Roberts B.Sc., A.R.C.S. Submitted for the Degree of Doctor of Philosophy of the University of London Imperial College of Science and Technology London 1982 2 ABSTRACT Electromigration is a common cause of failure of the aluminium thin film metallizations used in many microelectronic devices and circuits. The objective of the present work was to draw correlations between processing parameters, micro- structure and susceptibility to electromigration failure of vacuum-evaporated aluminium films on amorphous Si O^. The chemical composition of the Al - Si C>2 interface was examined using x-ray photoelectron spectroscopy, Auger electron spectroscopy and transmission electron microscopy and diffraction. The effects of substrate surface preparation and temperature on Al - Si O^ interfacial reaction were investigated. Reduction of the Si02 by the aluminium, resulting in the production of polycrystalline silicon and Tj - alumina, was found to occur under the conditions prevalent in many industrial metallization processes. The implications of Al-Si O2 reaction for device reliability are discussed. A range of techniques, including transmission and scanning electron microscopy and grazing incidence x-ray diffraction, were used to characterize the grain size, preferred orientation and surface topography of aluminium films deposited onto Si C>2 under various conditions. 1 yum thick aluminium films were found to have a ^111) fibre texture and the mean grain size ranged from less than 0.5yjm for deposition at 300 K, to ** 5 yum, for deposition at 675 K. Some thinner films were also examined, and trends in grain size and orientation with thickness were established.
    [Show full text]
  • State-Of-The-Art Report on Structural Materials Modelling
    Nuclear Science NEA/NSC/R(2016)5 May 2017 www.oecd-nea.org State-of-the-art Report on Structural Materials Modelling State-of-the-art Report on Structural Materials Modelling ORGANISATION FOR ECONOMIC CO-OPERATION AND DEVELOPMENT The OECD is a unique forum where the governments of 35 democracies work together to address the economic, social and environmental challenges of globalisation. The OECD is also at the forefront of efforts to understand and to help governments respond to new developments and concerns, such as corporate governance, the information economy and the challenges of an ageing population. The Organisation provides a setting where governments can compare policy experiences, seek answers to common problems, identify good practice and work to co-ordinate domestic and international policies. The OECD member countries are: Australia, Austria, Belgium, Canada, Chile, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Israel, Italy, Japan, Korea, Latvia, Luxembourg, Mexico, the Netherlands, New Zealand, Norway, Poland, Portugal, the Slovak Republic, Slovenia, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States. The European Commission takes part in the work of the OECD. OECD Publishing disseminates widely the results of the Organisation’s statistics gathering and research on economic, social and environmental issues, as well as the conventions, guidelines and standards agreed by its members. NUCLEAR ENERGY AGENCY The OECD Nuclear Energy Agency (NEA) was established on 1 February 1958. Current NEA membership consists of 31 countries: Australia, Austria, Belgium, Canada, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Japan, Korea, Luxembourg, Mexico, the Netherlands, Norway, Poland, Portugal, Russia, the Slovak Republic, Slovenia, Spain, Sweden, Switzerland, Turkey, the United Kingdom and the United States.
    [Show full text]
  • Hectorite: Synthesis, Modification, Assembly and Applications Jing Zhang, Chun Hui Zhou, Sabine Petit, Hao Zhang
    Hectorite: Synthesis, modification, assembly and applications Jing Zhang, Chun Hui Zhou, Sabine Petit, Hao Zhang To cite this version: Jing Zhang, Chun Hui Zhou, Sabine Petit, Hao Zhang. Hectorite: Synthesis, modification, assembly and applications. Applied Clay Science, Elsevier, 2019, 177, pp.114-138. 10.1016/j.clay.2019.05.001. hal-02363196 HAL Id: hal-02363196 https://hal-cnrs.archives-ouvertes.fr/hal-02363196 Submitted on 2 Dec 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. 1 Hectorite：Synthesis, Modification, Assembly and Applications 2 3 Jing Zhanga, Chun Hui Zhoua,b,c*, Sabine Petitd, Hao Zhanga 4 5 a Research Group for Advanced Materials & Sustainable Catalysis (AMSC), State Key Laboratory 6 Breeding Base of Green Chemistry-Synthesis Technology, College of Chemical Engineering, Zhejiang 7 University of Technology, Hangzhou 310032, China 8 b Key Laboratory of Clay Minerals of Ministry of Land and Resources of the People's Republic of 9 China, Engineering Research Center of Non-metallic Minerals of Zhejiang Province, Zhejiang Institute 10 of Geology and Mineral Resource, Hangzhou 310007, China 11 c Qing Yang Institute for Industrial Minerals, You Hua, Qing Yang, Chi Zhou 242804, China 12 d Institut de Chimie des Milieux et Matériaux de Poitiers (IC2MP), UMR 7285 CNRS, Université de 13 Poitiers, Poitiers Cedex 9, France 14 15 Correspondence to: Prof.
    [Show full text]
  • SPECIAL EDITION Table of Contents the RAIN EVENTS: SPECIAL EDITION UNDERSTANDING POLLUTANTS
    SPECIAL EDITION Table of Contents THE RAIN EVENTS: SPECIAL EDITION UNDERSTANDING POLLUTANTS The Understanding Pollutants series was originally published in The Rain Events newsletter, starting in January 2017, and finishing in October 2018. In this special edition, we’ve compiled all twelve articles into one easy-reference publication. Letter from the editor 3 The Three Basics pH 4 Oil and Grease 5 Total Suspended Solids 6 Metals Zinc 7 Copper 8 Magnesium 9 Iron 10 Aluminium 11 Lead 12 Wet Chemistry BOD and COD 13 Ammonia 14 Nitrate + Nitrite as N 15 References and Endnotes 16 The Rain Events is a publication of WGR Southwest, Inc. Do not duplicate, sell or distribute without express permission of the publisher. All content © 2018 WGR Southwest, Inc. All rights reserved. 2 Letter from the editor THE RAIN EVENTS: SPECIAL EDITION UNDERSTANDING POLLUTANTS Chemistry is daunting. All those formulas, calculations, and experiments have a way of giving most normal people a headache. But hiding behind the numbers is some information that’s actually useful and practical. In the past twelve editions of The Rain Events, we’ve attempted to take these chemistry concepts and distill them into something that the average person can readily understand. We received tons of positive comments about this series of newsletters. (Apparently, we weren’t the only ones scratching our heads about chemistry.) So, our staff put together a compilation of the Understanding Pollutants series, John Teravskis, CPESC, QISP creating what we hope is not only a beautiful special issue, but Lead Editor Senior Compliance Specialist a useful reference for the working storm water professional.
    [Show full text]
  • Point Defects in Aln and Al-Rich Algan from First Principles
    ABSTRACT HARRIS, JOSHUA SIMON. Point Defects in AlN and Al-rich AlGaN from First Principles. (Under the direction of Douglas L. Irving.) Point defects and defect complexes in AlN and Al-rich AlGaN have been investigated using ab initio density functional theory (DFT) in three separate but related projects. First, oxygen and silicon defects in Al0.65Ga0.35N were examined using explicit random alloy sim- 1 ulations. The O−N acceptor was found to relax into one of many DX configurations, with formation energies strongly dependent on local chemistry. Trends in the formation ener- gies were identified and explained with simple arguments involving cation-oxygen bonds. +1 +1 ON and SiIII were found to relax into on-site configurations with little variation in forma- tion energies. Second, DFT simulations were used to explain the experimentally observed “compensation knee” in Si-doped AlN (whereby the Si donor becomes an acceptor at high doping levels). VAl + nSiAl complexes were demonstrated to be the key to a mechanistic understanding of the compensation knee. Using a Grand Canonical charge balance solver, the compensation knee was qualitatively reproduced from the results of DFT simulations. Additionally, a shift in optical emissions was predicted for the high and low doping limits, which was confirmed by photoluminescence measurements. Finally, phonon and thermal strain simulations were used to investigate the temperature-dependent properties of bulk AlN and common point defects in AlN (Si, O, C, and vacancies). A number of general trends were identified in finite-temperature properties which are common to all or many of the defects under study.
    [Show full text]
  • Download the Scanned
    American Mineralogist, Volume 78, pages1314-1319, 1993 NEW MINERAL NAMES* JonN L. Jlnrnon Department of Earth Sciences,University of Waterloo, Waterloo, Ontario N2L 3G1, Canada Dlvro A. VaNxo Department of Geology, Georgia State University, Atlanta, Georyia 30303, U.S.A. Bearthite* Cancrisilite* C. Chopin, F. Brunet, W. Gebert, O. Medenbach,E. Till- A.P. Khomyakov, E.I. Semenov, E.A. Pobedimskaya, manns(1993) Bearthite, CarAl[POo]r(OH), a new min- T.N. Nadezhina, R.K. Rastsvetaeva(1991) Cancrisilite eral from high-pressureterranes of the western Alps. Nar[AlrSirOro]COr.3HrO:A new mineral of the can- Schweiz.Mineral. Petrogr. Mitt., 73, l-9. crinite group. Zapiski Vses. Mineral. Obshch., 120(6), 80-84 (in Russian). Electron microprobe analysesof the holotype sample from the Monte Rosa massif, Z,ermatt Valley, Switzer- The reportedchemical composition is NarO 21.30,KrO land, gave CaO 33.04, SrO 3.53, MgO 0.12, FeO 0.03, 0.10,CaO 0.68, MnO 0.1l, FerO.0.33,AlrO3 24.42,5iO, AlrO3 15.91,CerO, 0.04, LarO30.03, SiO, 0.30, PrO, 43.11,CO2 4.82, SO3 0.36, HrO 5.01,sum 100.24wto/o, 44.32, SO30.01, F 0.48, Cl 0.02, sum (lessO = F, Cl) correspondingto (Nau.rIQorCao ,rFeo ooMgo or)"r ro(Alo,*o- 97.62wto/o, corresponding to (Ca3,oSro ,r)r, nu(Al, ,r- Si, 2o)",2ooo2o ,o(COr), r0(SOo)0 0o'2.79HrO, ideally NarAlr- Mgoor)"r 00(P3 eTsio 03)>o ooFo ,u, closeto the ideal formula SirOr4CO3.3HrO.Dissolves readily with effervescenceat CarAl[POo]r(OH), with OH confirmed by structural re- room temperature in l0o/oHCl, HNO3, and HrSOo.
    [Show full text]
  • Understanding Defects in Germanium and Silicon for Optoelectronic Energy Conversion by Neil Sunil Patel B.S., Georgia Institute of Technology (2009)
    Understanding Defects in Germanium and Silicon for Optoelectronic Energy Conversion by Neil Sunil Patel B.S., Georgia Institute of Technology (2009) Submitted to the Department of Materials Science and Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the MASSACHUSETTS INSTITUTE OF TECHNOLOGY June 2016 © Massachusetts Institute of Technology 2016. All rights reserved. Author.......................................................................... Department of Materials Science and Engineering May 17, 2016 Certified by . Lionel C. Kimerling Thomas Lord Professor of Materials Science and Engineering Thesis Supervisor Certified by . Anuradha M. Agarwal Principal Research Scientist, Materials Processing Center Thesis Supervisor Acceptedby..................................................................... Donald Sadoway Chairman, Department Committee on Graduate Theses Understanding Defects in Germanium and Silicon for Optoelectronic Energy Conversion by Neil Sunil Patel Submitted to the Department of Materials Science and Engineering on May 17, 2016, in partial fulfillment of the requirements for the degree of Doctor of Philosophy Abstract This thesis explores bulk and interface defects in germanium (Ge) and silicon (Si) with a focus on understanding the impact defect related bandgap states will have on optoelectronic applications. Optoelectronic devices are minority carrier devices and are particularly sensi- tive to defect states which can drastically reduce carrier lifetimes in small concentrations. We performed a study of defect states in Sb-doped germanium by generation of defects via irradiation followed by subsequent characterization of electronic properties via deep- level transient spectroscopy (DLTS). Cobalt-60 gamma rays were used to generate isolated vacancies and interstitials which diffuse and react with impurities in the material toform four defect states (E37,E30,E22, and E21) in the upper half of the bandgap.
    [Show full text]
  • Structure of Cation Interstitial Defects in Nonstoichiometric Rutile L.A
    Structure of cation interstitial defects in nonstoichiometric rutile L.A. Bursill, M.G. Blanchin To cite this version: L.A. Bursill, M.G. Blanchin. Structure of cation interstitial defects in nonstoichiometric rutile. Journal de Physique Lettres, Edp sciences, 1983, 44 (4), pp.165-170. 10.1051/jphyslet:01983004404016500. jpa-00232175 HAL Id: jpa-00232175 https://hal.archives-ouvertes.fr/jpa-00232175 Submitted on 1 Jan 1983 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. J. Physique - LETTRES 44 (1983) L-165 - L-170 15 FÉVRIER 1983, L-165 Classification Physics Abstracts 61. 70B - 61. 70P - 61. 70Y Structure of cation interstitial defects in nonstoichiometric rutile L. A. Bursill (*) and M. G. Blanchin Département de Physique des Matériaux (**), Université Claude Bernard, Lyon I, 43, Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, France (Re~u le 16 aofit 1982, revise le 14 decembre, accepte le 3 janvier 1983) Résumé. - On présente ici de nouveaux modèles de défauts interstitiels pour accommoder la non- stoechiométrie du rutile peu réduit TiO2-x. Ces défauts consistent en des arrangements linéaires, le long de directions [100] ou [010], de paires de cations trivalents situés au centre d’octaèdres d’oxygène ayant une face en commun.
    [Show full text]
  • Energetics of Point Defects in Aluminum Via Orbital-Free Density Functional Theory
    Energetics of point defects in aluminum via orbital-free density functional theory Ruizhi Qiua, Haiyan Lua, Bingyun Aoa, Li Huanga, Tao Tanga, Piheng Chena aScience and Technology on Surface Physics and Chemistry Laboratory, Mianyang 621908, Sichuan, P.R. China Abstract The formation and migration energies for various point defects, including va- cancies and self-interstitials in aluminum are reinvestigated systematically using the supercell approximation in the framework of orbital-free density functional theory. In particular, the finite-size effects and the accuracy of various kinetic energy density functionals are examined. The calculated results suggest that the errors due to the finite-size effect decrease exponentially upon enlarging the supercell. It is noteworthy that the formation energies of self-interstitials con- verge much slower than that of vacancy. With carefully chosen kinetic energy density functionals, the calculated results agree quite well with the available experimental data and those obtained by Kohn-Sham density functional theory which has exact kinetic term. Keywords: Formation energy, migration energy, point defects, orbital-free density functional theory, aluminum 1. Introduction Neutron and other energetic particles produced by nuclear reactions usu- ally induce significant changes in the physical properties of irradiated materials. Since the radiation defects are often very small and hence not readily accessible arXiv:1611.07631v1 [cond-mat.mtrl-sci] 23 Nov 2016 to an experimental observation, many atomic-, mesoscopic-, and continuum- ∗Corresponding author Email address: [email protected] (Li Huang) Preprint submitted to Journal of Nuclear Materials November 24, 2016 level models have been developed to understand the irradiation effect on ma- terials in the past [1{4].
    [Show full text]
  • PGE in the Modern Hydrotherms of Kudryavy Volcano (Kuril Islands)
    PGE in the Modern Hydrotherms of Kudryavy Volcano (Kuril Islands) Vadim Distler, Marina Yudovskaya, Ilya Chaplygin and Vladimir Znamensky Institute of Geology of Ore Deposits, Petrography, Mineralogy, and Geochemistry (IGEM), Russian Academy of Sciences e-mail: [email protected] Introduction sphalerite with accompanying silicates, barite, The behavior of platinum group elements anhydrite, chlorides of sodium and potassium. (PGE) in the active volcanoes’ hydrothermal The Main Field, characterized by the systems was studied in the hydrothermal fields of highest temperature of fluid, is located in the center Kudryavy volcano situated in the Iturup Island (the of the main volcano’s crater. This summer the Kuril island Arc of the Russian Far East) (Fig.1). measured temperature was 870oC whereas the This research was carried out owing to an increased maximal measured temperature was 940oC. amount of the data on PGE mineralization in Specific mineralization of this Field consists of hydrothermal conditions. Previous research of various lead-bismuth salfosalts. A basic peculiarity Korzhinsky et al. (1996) as well as our preliminary of the Rhenium Field is a wide spread occurrence data shows that PGE is present in some products of of rhenium disulfide (ReS2), Zn-Cd-In sulfides with this volcano’s fumarolic activity. The most increased Sn and Se contents and also lead-bismuth significant fact established by the time was the salfosalts. The maximal temperature of the ore- detection of native platinum in the high- forming fluid is 500oC. Typical gangue minerals are temperature fluid’s sublimates precipitated in silica diopside, wollastonite, garnet and pyroxene. tubes with the high gradient.
    [Show full text]
  • Diamonds, Native Elements and Metal Alloys from Chromitites of the Ray-Iz Ophiolite of the Polar Urals
    GR-01291; No of Pages 27 Gondwana Research xxx (2014) xxx–xxx Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr Diamonds, native elements and metal alloys from chromitites of the Ray-Iz ophiolite of the Polar Urals Jingsui Yang a,⁎,FancongMenga, Xiangzhen Xu a,PaulT.Robinsona,YildirimDilekb, Alexander B. Makeyev c, Richard Wirth d,MichaelWiedenbeckd, William L. Griffin e,JohnClifff a CARMA, State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China b Department of Geology and Environmental Earth Science, Miami University, Oxford, OH 45056, USA c Institute of Geology, Komi Scientific Center, Ural Division, Russian Academy of Sciences, Pervomaiskayaul. 54, Syktyvkar, 167982 Komi Republic, Russia d Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, D14473 Potsdam, Germany e GEMOC, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia f CMCA, The University of Western Australia, Crawley, WA 6009, Australia article info abstract Article history: Diamonds and a wide range of unusual minerals were originally discovered from the chromitite and peridotite of Received 19 October 2013 the Luobusa ophiolite along the Yarlong–Zangbu suture zone in southern Tibet. To test whether this was a unique Received in revised form 14 July 2014 occurrence or whether such minerals were present in other ophiolites, we investigated the Ray-Iz massif of the Accepted 14 July 2014 early Paleozoic Voikar–Syninsk ophiolite belt in the Polar Urals (Russia) for a comparative study. Over 60 mineral Available online xxxx species, including diamond, moissanite, native elements and metal alloys have been separated from ~1500 kg of Keywords: chromitite collected from two orebodies in the Ray-Iz ophiolite.
    [Show full text]
  • Defects in Silicon Crystals - Some Very Basic Remarks
    CERN, TA1/SSD coffee-meeting 11.6.2004 Defects in silicon crystals - Some very basic remarks - Michael Moll CERN - Geneva - Switzerland People are like crystals. It is the defects in them that make them interesting. Sir F.Charles Frank Perfection has one grave defect : it is apt to be dull William Somerset Maugham · Defects give silicon crystals new properties · These properties can be useful (e.g. doping, defect engineering) or not (e.g. radiation damage, metal contaminations) CERN, TA1/SSD coffee meeting 11.6.2004 Outline • Silicon and Silicon crystal structure Easy • Defect types in silicon crystals level • Silicon doping (Dopants = Defects) • Radiation induced defects More • What are defects doing to detectors? difficult level • How to measure defects? • Coffee } Relax level CERN TA1/SSD Silicon Atomic number = 14 Atomic mass 28.0855 amu · Most abundant solid element on earth 50% O, 26% Si, 8% Al, 5% Fe, 3% Ca, ... · 90% of earth’s crust is composed of silica (SiO2) and silicate ! ? Very pure sand or quartz Silicon (e.g. from Australia or Nova Scotia in Canada) » 99% SiO2 Another coffee meeting ? » 1% Al2O3, Fe2O3, TiO2 (CaO,MgO) Michael Moll – TA1/SD meeting – June 2004 -3- CERN TA1/SSD Unit Cell in 3-D Structure Unit cell Michael Moll – TA1/SD meeting – June 2004 -4- CERN TA1/SSD Faced-centered Cubic (FCC) Unit Cell Michael Moll – TA1/SD meeting – June 2004 -5- CERN TA1/SSD Silicon Crystal Structure Silicon has the basic diamond crystal Basic FCC Cell Merged FCC Cells structure: two merged FCC cells offset by a/4 in x, y and z Omitting atoms Bonding of Atoms outside Cell Michael Moll – TA1/SD meeting – June 2004 -6- CERN TA1/SSD Silicon Crystal Structure Link: BC8 Structure of Silicon Link: Silicon lattice (wrl) Link: Silicon lattice with bonds (wrl) Silicon crystallizes in the same pattern as Diamond, in a structure called "two interpenetrating face-centered cubic" primitive lattices.
    [Show full text]