DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Density Functional Theory study of defects in zirconolite Jack Mulroue.

Slides:

Advertisements

Similar presentations

Advertisements

Thermodynamics of oxygen defective TiO2-x : The Magneli phases.

CECAM workshop on Actinides, Manchester, June DFT+U calculations of the electronic structure of perfect and defective PuO 2 Eugene Kotomin and Denis.

Peter De á k Challenges for ab initio defect modeling. EMRS Symposium I, Challenges for ab initio defect modeling Peter.

Thermodynamics of Oxygen Defective Magnéli Phases in Rutile: A First Principles Study Leandro Liborio and Nicholas Harrison Department of Chemistry, Imperial.

Ab INITIO CALCULATIONS OF HYDROGEN IMPURITES IN ZnO A. Useinov 1, A. Sorokin 2, Y.F. Zhukovskii 2, E. A. Kotomin 2, F. Abuova 1, A.T. Akilbekov 1, J. Purans.

Imperfection in Solids

+ Ionic Bonds and Ionic Compounds Forming Compounds from Ions.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Effects of Zinc Addition on the Structure of Sodium Silicate Glass.

How To Get DFT To Work for CeO 2 Christopher Castleton 1, Jolla Kullgren 2, Carsten Müller 3, David Muñoz Ramo 4, Amy Green 1 & Kersti Hermansson 2 1.

Lattice defects in oxides.

Computational Solid State Chemistry 2 SSI-18 Workshop 2011 Rob Jackson

Ab initio Calculations of Interfacial Structure and Dynamics in Fuel Cell Membranes Ata Roudgar, Sudha P. Narasimachary and Michael Eikerling Department.

Lecture Notes II Defect Chemistry

What is e-Science? e-Science refers to large scale science that will increasingly be carried out through distributed global collaborations enabled by the.

The total energy as a function of collective coordinates, ,  for upright and tilted structures are plotted. Two types of frequency spectrum are calculated:

Ab initio study of the diffusion of Mn through GaN Johann von Pezold Atomistic Simulation Group Department of Materials Science University of Cambridge.

First Principles Calculations of Complex Oxide Perovskites David-Alexander Robinson Sch., Theoretical Physics, The University of Dublin, Trinity College.

Lecture 5 (9/20/2006) Crystal Chemistry Part 4: Compositional Variation of Minerals Solid Solution Mineral Formula Calculations Graphical Representation.

ATOMIC MASS & AVERAGE ATOMIC MASS

Chemical Bonding September 4, What do we already know? Where are protons? Neutrons? Electrons? What is an electron shell? How many electrons fill.

 Recent studies show that a single Ti atom coated on a single-walled nanotube (SWNT) and C 60 fullerene could bind up to four hydrogen molecules [1-2].

Advances in computational studies of energy materials by C. R. A. Catlow, Z. X. Guo, M. Miskufova, S. A. Shevlin, A. G. H. Smith, A. A. Sokol, A. Walsh,

The Nuts and Bolts of First-Principles Simulation Durham, 6th-13th December : DFT Plane Wave Pseudopotential versus Other Approaches CASTEP Developers’

Computer modelling of the concentration dependence of doping in solid state ionic materials Robert A Jackson School of Physical and Geographical Sciences,

Ionic Conductors: Characterisation of Defect Structure Lecture 15 Total scattering analysis Dr. I. Abrahams Queen Mary University of London Lectures co-financed.

Atomic scale understandings on hydrogen behavior in Li 2 O - toward a multi-scale modeling - Satoru Tanaka, Takuji Oda and Yasuhisa Oya The University.

Modelling of Radiation Induced Vacancy-Interstitial Clusters Ernestas Žąsinas & Juozas Vaitkus Institute of Applied Research, Vilnius University, Vilnius,

Recent related paper: Solid State Phenomena, (2011) 313 Positron Annihilation on Point Defects in n-FZ –Si:P Single Crystals Irradiated With 15.

First-principles Investigations on Vacancy of Ge in Strained Condition Jung-Hae Choi, Seung-Cheol Lee, and Kwang-Ryeol Lee Computational Science Center.

Chapter 7 Atomic Energies and Periodicity Department of Chemistry and Biochemistry Seton Hall University.

Electron Configurations for the Ions of Transition Metals & Main Group Elements Chemistry 11.

Using computer modelling to help design materials for optical applications Robert A Jackson Chemical & Forensic Sciences School of Physical & Geographical.

First-principles Study on Intrinsic Defects of Ge in Strained Condition Jung-Hae Choi, Seung-Cheol Lee, and Kwang-Ryeol Lee Computational Science Center.

Calculations of Electronic Structure of Defective ZnO: the impact of Symmetry and Phonons A.V. Sorokin, D. Gryaznov, Yu.F. Zhukovskii, E.A. Kotomin, J.

3/6/ APS March Meeting1 Structure and interface properties of the electrolyte material Li 4 P 2 S 6 * Zachary D. Hood, a Cameron M. Kates, b,c.

The Electronic Structure of the Ti4O7 Magneli Phase

DEFECTS IN CRYSTALS Point defects Line defects Surface Imperfections.

Effect of Oxygen Vacancies and Interfacial Oxygen Concentration on Local Structure and Band Offsets in a Model Metal-HfO 2 - SiO 2 -Si Gate Stack Eric.

Australian Nuclear Science & Technology Organisation Simulating radiation damage in quaternary oxides Bronwyn Thomas, Nigel Marks, Bruce Begg, René Corrales,

Model for B Site Ordering in PMN Eric Cockayne Benjamin P. Burton Material Measurement Laboratory, NIST, Gaithersburg.

(AHSS) Development of Nano-acicular Duplex Steels- CMMI David C. Van Aken, Missouri University of Science and Technology, DMR Overview:

First-Principles Based Prediction of High-Temperature Defect Chemistry and Conductivity of TiO 2 Elizabeth C. Dickey, Pennsylvania State Univ University.

Materials Science Chapter 4 Disorder in solid Phases.

1 4.1 Introduction to CASTEP (1)  CASTEP is a state-of-the-art quantum mechanics-based program designed specifically for solid-state materials science.

CCMGCCMGCCMGCCMGCCMGCCMGCCMGCCMG Ji-Hui Yang, Shiyou Chen, Wan-Jian Yin, and X.G. Gong Department of Physics and MOE laboratory for computational physical.

Material science & Metallurgy L D College of Engineering Mechanical Engineering 1.

Emission Mössbauer spectroscopy of advanced materials for opto- and nano-electronics Spokepersons: Haraldur Páll Gunnlaugsson Sveinn Ólafsson Contact person:

Kristian Berland, Simen N. H. Eliassen,

BY SELLAVEL E (CA15M006) Guided By Prof.B.Viswanathan

Modelling and theory of systems relevant to nuclear waste processing

Simplest Inorganic Double-Helix Structures

Schrödinger's Cat A cat is placed in an airtight box with an oxygen supply and with a glass vial containing cyanide gas to be released if a radiation detector.

Half-Metallic Ferromagnetism in Fe-doped Zn3P2 From First-Principles Calculations G. JAI GANESH and S. MATHI JAYA Materials Science Group, Indira Gandhi.

DEFECTS IN CRYSTALS Point defects Line defects Surface Imperfections.

of interfaces in glass/crystal composites for nuclear wasteforms

DFT simulations of Li-ion conductor Li2(OH)Cl

Effects of Si on the Electronic Properties of the Clathrates

Imperfections in Solids

Understanding Electrons

Chapter 12 Solids and Modern Materials

Chapter 12 – Solids and Modern Materials

Electronic Structure and First Principles Theory

Prof. Sanjay. V. Khare Department of Physics and Astronomy,

SOLID STATE CHMISTRY By: Dr. Aamarpali

Structure & Properties of Matter

Chemistry Chapter 7 Chemical Bonding.

Metastability of the boron-vacancy complex (C center) in silicon: A hybrid functional study Cecil Ouma and Walter Meyer Department of Physics, University.

Computational Materials Science Group

The Atomic-scale Structure of the SiO2-Si(100) Interface

Presentation transcript:

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Density Functional Theory study of defects in zirconolite Jack Mulroue University College London 11/13 April 2011 Huddersfield

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Background for zirconoilite Zirconolite is the proposed ceramic encapsulent for geological disposal. Zirconolite is able to accommodate Pu and U as well as Hf and Gd into its crystal lattice. Actinide bearing phase in SYNROC, glass ceramics and single phase waste forms. Geological disposal options for HLW and spent fuel - NDA

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal CaZrTi 2 O 7 Monoclinic crystal structure ( α≠ 90 °, β=γ= 90 ° ) Structure comprises of 4 and 6 coordinated Ti layers separated by layers of alternating Ca and Zr ions.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal VASP –Periodic plain wave DFT code PBE exchange and correlation Γ point sampling of the Brillouin zone PAW pseudopotentials 176 ion cell

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Calculated bulk properties Band gap of 2.8 eV (3.6 eV experimental) Lattice parameters Lattice parameter DFT (Å) Experimental (Å) % Error a b c Miseki et al. - Chemistry Letters 38, 2009 Rossell – Nature 283, 1980

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Effect of stoichiometry Zirconolite is able to exist in a range of stoichiometries. CaZr x Ti 3-x O 7 where 0.80 < x < 1.37 Experiments observe 5 fold coordinated Ti polyhedra instead of 4 fold coordinated Ti found in the perfect structure.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Excess of Ti CaZr Ti O 7 The substituted Ti is 5 fold coordinated in the Zr site. Has no effect on the coordination of the four 4 fold coordinated Ti polyhedra.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Excess of Zr CaZr Ti O 7 The two 4 fold coordinated Ti polyhedra in the same row as the substituted Zr become 5 coordinated. Therefore to remove all 4 fold coordinated Ti polyhedra, with x = 1.25, the two Zr must be in different Ti layers.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Point defects in zirconolite The point defects have been studied to gain a fundamental understanding into defect behaviour, to allow for more accurate predictions on the long term durability of the waste form. Each defect has been studied in the various charge states, from 0 to formal charge.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Oxygen vacancies 4 of the 7 oxygen environments have been studied. The 2 excess electrons generated from the neutral oxygen vacancy localised on 2 Ti ions. The singly charged vacancy localises the excess electron on the Ti ion it was coordinated too. Similar behaviour is observed in anatase (TiO 2 ).

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Titanium vacancies The defect structure has a significant dependence on the chemical environment of the Ti. Vacancy in the 6 fold coordinated chains, results in the formation of an O 2 molecule in certain charge states and a 5 coordinated Ti in others. A vacancy of the other 6 coordinated Ti, results in the 4 coordinated Ti becoming 6 coordinated. The vacant 4 coordinated Ti resulted in the creation different numbers of 5 coordinated Ti in different charge states.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Ca and Zr vacancies The Ca vacancy results in distortion around the vacancy site. The neutral Zr vacancy results in the formation of an O 2 molecule. The singly charged vacancy results in the creation of 5 coordinated at the expense of a 6 coordinated Ti. The higher charge states results in distortion around the vacancy site.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Locating the interstitials The interstitial sites were studied using random structure analysis, based on the AIRSS method. The 88 ion unit cell was optimised using soft oxygen pseudopotentials, with the cell parameters fixed to the experimental lattice vectors. The interstitial ion was then added with randomly assigned coordinates and all the ions were allowed to relax. This was carried out 100 times for each interstitial. The lowest energy structure was then placed inside the 1x2x1 supercell to obtain the interstitial structure.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Oxygen interstitials The oxygen interstitial can only exist in two charge states, 0 and -1. The neutral interstitial forms an oxygen dumb-bell with a lattice oxygen at high interstitial concentrations. However at lower concentrations the interstitial causes two 7 coordinated Ti and a 5 coordinated Ti. The singly charged interstitial produces a 5 coordinated Ti polyhedron caused by displacement of two lattice oxygen ions on the same polyhedron.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Ca and Ti interstitials The cation interstitials were found only to exist in the +2 charge state. Both Ca and Ti interstitials reside within the channels which run through the crystal.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Zr interstitials The most stable interstitial configuration was the Zr ion substituting for a Ti lattice ion. Bond length increase in the polyhedron due to substitution. This configuration was 0.27 eV more stable than the Zr remaining as the interstitial located in the channel.

DIAMOND Decommissioning, Immobilisation and Management of Nuclear Wastes for Disposal Conclusions The presents of non-stoichiometry and vacancies in the experimental samples causes the difference in coordination of the Ti polyhedron. O 2 molecules could form at vacancy sites within the lattice. The substitution caused by the Zr interstitial may have a significant effect on the recovery of the lattice from an irradiation event. Require more fundamental experimental work to allow accuracy of our models to assessed.