Search query: First-principles calculations for point defects in solids

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abstract: Point defects and impurities strongly affect the physical properties of materials and have a decisive impact on their performance in applications. First principles calculations have emerged as a powerful approach that complements experiments and can serve as a predictive tool in the identification and characterization of defects. The theoretical modeling of point defects in crystalline materials by means of electronic structure calculations, with an emphasis on approaches based on density functional theory (DFT) is reviewed. A general thermodynamic formalism is laid down to investigate the physical properties of point defects independent of the materials class (semiconductors, insulators, and metals) indicating how the relevant thermodynamic quantities, such as formation energy, entropy, and excess volume, can be obtained from electronic structure calculations. Practical aspects such as the supercell approach and efficient strategies to extrapolate to the isolated defect or dilute limit are discussed. Recent advances in tractable approximations to the exchange correlation functional \mathrm{DFT}+U$ hybrid functionals) and approaches beyond DFT are highlighted. These advances have largely removed the long standing uncertainty of defect formation energies in semiconductors and insulators due to the failure of standard DFT to reproduce band gaps. Two case studies illustrate how such calculations provide new insight into the physics and role of point defects in real materials.
author_names: Christoph Freysoldt

Blazej Grabowski

Tilmann Hickel

Jorg Neugebauer

Georg Kresse

Anderson Janotti

Chris G van de Walle
title: First principles calculations for point defects in solids
year: 2014

abstract: A first principles calculation for uranium dioxide (UO2) in an antiferromagnetic structure with four types of point defects, uranium vacancy, oxygen vacancy, uranium interstitial, and oxygen interstitial, has been performed by the projector augmented wave method with generalized gradient approximation combined with the Hubbard U correction. Defect formation energies are estimated under lattice relaxation for supercells containing 1, 2, and 8 unit cells of UO2. The electronic structure, the atomic displacement and the stability of defected systems are obtained, and the effects of cell sizes on these properties are discussed. The results form a self consistent dataset of formation energies and atomic distance variations of various point defects in UO2 with relatively high precision. We show that a supercell with 8 UO2 unit cells or larger is necessary to investigate the defect behavior with reliable precision, since point defects have a wide ranging effect, not only on the first nearest neighbor atoms of the defect, but on the second neighbors and on more distant atoms. [doi:10.2320/matertrans.47.2651]
author_names: Misako Iwasawa

Ying Chen

Yasunori Kaneta

Toshiharu Ohnuma

Hua Y Geng

Motoyasu Kinoshita
title: First Principles Calculation of Point Defects in Uranium Dioxide
year: 2006

abstract: Uranium (U) exhibits a high temperature body centered cubic (bcc) allotrope that is often stabilized by alloying with transition metals such as Zr, Mo, and Nb for technological applications. One such application involves U Zr as nuclear fuel, where radiation damage and diffusion (processes heavily dependent on point defects) are of vital importance. Several systems of U are examined within a density functional theory framework utilizing projector augmented wave pseudopotentials. Two separate generalized gradient approximations of the exchange correlation are used to calculate defect properties and are compared. The bulk modulus, the lattice constant, and the Birch Murnaghan equation of state for the defect free bcc uranium allotrope are calculated. Defect parameters calculated include energies of formation of vacancies in the a and g allotropes, as well as self interstitials, Zr interstitials, and Zr substitutional defects for the g allotrope. The results for vacancies agree very well with experimental and previous computational studies. The most probable self interstitial site in g U is the (110) dumbbell, and the most probable defect location for dilute Zr in g U is the substitutional site. This is the first detailed study of self defects in the bcc allotrope of U and also the first comprehensive study of dilute Zr defects in g U.
author_names: Benjamin W Beeler

Brian Good

Sergey N Rashkeev

Chaitanya Deo

Michael I Baskes

Maria A Okuniewski
title: First principles calculations for defects in U.
venue: Journal of physics. Condensed matter an Institute of Physics journal
year: 2010

abstract: Abstract The CASTEP code for first principles electronic structure calculations will be described. A brief, non technical overview will be given and some of the features and capabilities highlighted. Some features which are unique to CASTEP will be described and near future development plans outlined.
author_names: Stewart J Clark

Matthew D Segall

Chris J Pickard

Philip Hasnip

Matt Probert

Keith Refson

Mike C Payne
title: First principles methods using CASTEP
year: 2005

abstract: First principles calculations have evolved from mere aids in explaining and supporting experiments to powerful tools for predicting new materials and their properties. In the first part of this review we describe the state of the art computational methodology for calculating the structure and energetics of point defects and impurities in semiconductors. We will pay particular attention to computational aspects which are unique to defects or impurities, such as how to deal with charge states and how to describe and interpret transition levels. In the second part of the review we will illustrate these capabilities with examples for defects and impurities in nitride semiconductors. Point defects have traditionally been considered to play a major role in wide band gap semiconductors, and first principles calculations have been particularly helpful in elucidating the issues. Specifically, calculations have shown that the unintentional n type conductivity that has often been observed in as grown GaN cannot be a.
author_names: Chris G van de Walle

Jorg Neugebauer
title: First principles calculations for defects and impurities: Applications to III nitrides
year: 2004

abstract: Abstract The title problem concerns two isotropic phases firmly bonded together to form a mixture with any concentrations. An elementary account of several theoretical methods of attack is given, among them the derivation of inequalities between various moduli. The approach is completely general and exact. Additionally, the problem is fully solved when the phases have equal rigidities but different compressibilities, the geometry being entirely arbitrary.
author_names: Rodney Hill
title: Elastic properties of reinforced solids: some theoretical principles
year: 1963

abstract: Preface Numerical simulation of intergranular and transgranular crack propagation in ferroelectric polycrystals Microstructure and stray electric fields at surface cracks in ferroelectrics Double kink mechanisms for discrete dislocations in BCC crystals The expanding spherical inhomogeneity with transformation strain A new model of damage: a moving thick layer approach On configurational forces at boundaries in fracture mechanics HotQC simulation of nanovoid growth under tension in copper Coupled phase transformations and plasticity as a field theory of deformation incompatibility Continuum strain gradient elasticity from discrete valence force field theory for diamond like crystals
author_names: Toshio Mura

D M Barnett
title: Micromechanics of defects in solids
year: 1982

abstract: The first principles calculations have been performed to investigate the ground state properties of monoperiodic boron nitride (BN) TiO2, and SrTiO3 single walled nanotubes (SW NTs) containing extrinsic point defects. The hybrid exchange correlation functionals PBE, B3LYP, and B3PW within the framework of density functional theory (DFT) have been applied for large scale ab initio calculations on NTs with the following substitutional impurities: AlB, PN, GaB, AsN, InB, and SbN in the BN NT, as well as CO, NO, SO, and FeTi in the TiO2 and SrTiO3 NTs, respectively. The variations in formation energies obtained for equilibrium defective nanostructures allow us to predict the most stable compositions, irrespective of the changes in growth conditions. The changes in the electronic structure are analyzed to show the extent of localization of the midgap states induced by defects. Finally, the electronic charge redistribution was calculated in order to explore the intermolecular properties, which show how the reactivity of the NTs under study was affected by doping and orbital hybridization.
author_names: Yuri F Zhukovskii

Sergei Piskunov

Jevgenijs Begens

Jurijs Kazerovskis

Oleg Lisovski
title: First principles calculations of point defects in inorganic nanotubes
year: 2013

abstract: The characterization of native point defects in ZnO is still a question of debate. For example, experimental evidence for ZnO with an excess of Zn is inconclusive as to whether the dominant defects are metal interstitials or oxygen vacancies. This information is essential to understand the behavior of the material and to tailor its numerous technological applications. We use the first principles pseudopotential method to determine the electronic structure, atomic geometry, and formation energy of native point defects in ZnO. Interstitials, vacancies, and antisites in their relevant charge states are considered and the effects of dopants are also discussed. The results show that both the Zn and O vacancies are the relevant defects in ZnO. We also propose a possible transition mechanism and defect center responsible for the experimentally observed green luminescence.
author_names: Adrian Kohan

Gerbrand Ceder

Dane Morgan

Chris G van de Walle
title: First principles study of native point defects in ZnO
year: 2000

abstract: Abstract We discuss the present status of the first principles electronic structure calculations for defect energies in metals. The calculations apply density functional theory in the generalized gradient approximation of Perdew and Wang, together with a full potential version of Korringa Kohn Rostoker Green's function method, developed by the Julich group. It is shown that: (1) the present calculations reproduce very well the experimental results for vacancy formation energies in metals, as well as the bulk properties such as equilibrium lattice parameters and bulk moduli of metals; and (2) the type of the phase diagram of a binary A B alloy can be characterized by the interaction energies between a pair of impurity B (A) atoms in the host metal A (B) The observed temperature dependence of the solid solubility limit of Rh in Pd is also reproduced very well by the free energy calculations based on the cluster variation method with the pair (up to the eighth neighbor) and many body (up to a tetrahedron of first nearest neighbors) interaction energies, all of which are determined by the present first principles calculations.
author_names: Mitsuhiro Asato

Toshiya Mizuno

Toshiharu Hoshino

K Masuda-Jindo

Kazuto Kawakami
title: First principles calculations for point defect energies in metals and phase diagrams of binary alloys
year: 2001