scholarly journals Atomistic Simulation of Intrinsic Defects and Trivalent and Tetravalent Ion Doping in Hydroxyapatite

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Ricardo D. S. Santos ◽  
Marcos V. dos S. Rezende
Keyword(s):  
Atomistic Simulation ◽  
Charge Compensation ◽  
Intrinsic Defect ◽  
Intrinsic Defects ◽  
Simulation Techniques ◽  
Ion Doping ◽  
Key Issues

Atomistic simulation techniques have been employed in order to investigate key issues related to intrinsic defects and a variety of dopants from trivalent and tetravalent ions. The most favorable intrinsic defect is determined to be a scheme involving calcium and hydroxyl vacancies. It is found that trivalent ions have an energetic preference for the Ca site, while tetravalent ions can enter P sites. Charge compensation is predicted to occur basically via three schemes. In general, the charge compensation via the formation of calcium vacancies is more favorable. Trivalent dopant ions are more stable than tetravalent dopants.

scholarly journals Defect, Diffusion and Dopant Properties of NaNiO2: Atomistic Simulation Study

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3094 ◽  
Author(s):  
Ruwani Kaushalya ◽  
Poobalasuntharam Iyngaran ◽  
Navaratnarajah Kuganathan ◽  
Alexander Chroneos
Keyword(s):  
Atomistic Simulation ◽  
High Capacity ◽  
Sodium Ion ◽  
Intrinsic Defect ◽  
Sodium Ion Batteries ◽  
Ion Diffusion ◽  
Defect Diffusion ◽  
Simulation Techniques ◽  
Defect Process ◽  
Isovalent Dopant

Sodium nickelate, NaNiO2, is a candidate cathode material for sodium ion batteries due to its high volumetric and gravimetric energy density. The use of atomistic simulation techniques allows the examination of the defect energetics, Na-ion diffusion and dopant properties within the crystal. Here, we show that the lowest energy intrinsic defect process is the Na-Ni anti-site. The Na Frenkel, which introduces Na vacancies in the lattice, is found to be the second most favourable defect process and this process is higher in energy only by 0.16 eV than the anti-site defect. Favourable Na-ion diffusion barrier of 0.67 eV in the ab plane indicates that the Na-ion diffusion in this material is relatively fast. Favourable divalent dopant on the Ni site is Co2+ that increases additional Na, leading to high capacity. The formation of Na vacancies can be facilitated by doping Ti4+ on the Ni site. The promising isovalent dopant on the Ni site is Ga3+.

scholarly journals Atomistic Simulations of the Defect Chemistry and Self-Diffusion of Li-ion in LiAlO2

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2895 ◽  
Author(s):  
N. Kuganathan ◽  
J. Dark ◽  
E.N. Sgourou ◽  
Y. Panayiotatos ◽  
A. Chroneos
Keyword(s):  
Atomistic Simulation ◽  
Three Dimensional ◽  
Atomistic Simulations ◽  
Intrinsic Defect ◽  
Lithium Content ◽  
Frenkel Defect ◽  
Self Diffusion ◽  
Simulation Techniques ◽  
Lithium Diffusion ◽  
Li Ion

Lithium aluminate, LiAlO2, is a material that is presently being considered as a tritium breeder material in fusion reactors and coating material in Li-conducting electrodes. Here, we employ atomistic simulation techniques to show that the lowest energy intrinsic defect process is the cation anti-site defect (1.10 eV per defect). This was followed closely by the lithium Frenkel defect (1.44 eV per defect), which ensures a high lithium content in the material and inclination for lithium diffusion from formation of vacancies. Li self-diffusion is three dimensional and exhibits a curved pathway with a migration barrier of 0.53 eV. We considered a variety of dopants with charges +1 (Na, K and Rb), +2 (Mg, Ca, Sr and Ba), +3 (Ga, Fe, Co, Ni, Mn, Sc, Y and La) and +4 (Si, Ge, Ti, Zr and Ce) on the Al site. Dopants Mg2+ and Ge4+ can facilitate the formation of Li interstitials and Li vacancies, respectively. Trivalent dopants Fe3+, Ni3+ and Mn3+ prefer to occupy the Al site with exoergic solution energies meaning that they are candidate dopants for the synthesis of Li (Al, M) O2 (M = Fe, Ni and Mn) compounds.

scholarly journals A Computational Study of Defects, Li-Ion Migration and Dopants in Li2ZnSiO4 Polymorphs

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 563 ◽  
Author(s):  
Dilki Perera ◽  
Sashikesh Ganeshalingam ◽  
Navaratnarajah Kuganathan ◽  
Alexander Chroneos
Keyword(s):  
Long Range ◽  
Atomistic Simulation ◽  
Computational Study ◽  
Orthorhombic Phase ◽  
Activation Energies ◽  
Intrinsic Defect ◽  
Li Ion Batteries ◽  
Ion Migration ◽  
Simulation Techniques ◽  
Li Ion

Lithium zinc silicate, Li2ZnSiO4, is a promising ceramic solid electrolyte material for Li-ion batteries. In this study, atomistic simulation techniques were employed to examine intrinsic defect processes; long range Li-ion migration paths, together with activation energies; and candidate substitutional dopants at the Zn and the Si sites in both monoclinic and orthorhombic Li2ZnSiO4 phases. The Li-Zn anti-site defect is the most energetically favourable defect in both phases, suggesting that a small amount of cation mixing would be observed. The Li Frenkel is the second lowest energy process. Long range Li-ion migration is observed in the ac plane in the monoclinic phase and the bc plane in the orthorhombic phase with activation energies of 0.88 eV and 0.90 eV, respectively, suggesting that Li-ion diffusivities in both phases are moderate. Furthermore, we show that Fe3+ is a promising dopant to increase Li vacancies required for vacancy-mediated Li-ion migration, and that Al3+ is the best dopant to introduce additional Li in the lattice required for increasing the capacity of this material. The favourable isovalent dopants are Fe2+ at the Zn site and Ge4+ at the Si site.

A Perspective on Modeling Materials in Extreme Environments: Oxidation of Ultrahigh-Temperature Ceramics

MRS Bulletin ◽  
2006 ◽  
Vol 31 (5) ◽  
pp. 410-418 ◽  
Author(s):  
Angelo Bongiorno ◽  
Clemens J. Först ◽  
Rajiv K. Kalia ◽  
Ju Li ◽  
Jochen Marschall ◽  
...  
Keyword(s):  
Modeling And Simulation ◽  
Atomistic Simulation ◽  
Extreme Environments ◽  
Protective Layer ◽  
Ceramic Composites ◽  
Atomistic Modeling ◽  
Temperature Oxidation ◽  
Simulation Techniques ◽  
Oxidation Resistant ◽  
Ultrahigh Temperature

AbstractThe broader context of this discussion, based on a workshop where materials technologists and computational scientists engaged in a dialogue, is an awareness that modeling and simulation techniques and computational capabilities may have matured sufficiently to provide heretofore unavailable insights into the complex microstructural evolution of materials in extreme environments.As an example, this article examines the study of ultrahigh-temperature oxidation-resistant ceramics, through the combination of atomistic simulation and selected experiments.We describe a strategy to investigate oxygen transport through a multi-oxide scale—the protective layer of ultrahigh-temperature ceramic composites ZrB2-SiC and HfB2-SiC—by combining first-principles and atomistic modeling and simulation with selected experiments.

Ultrathin oxide films: CaO layers on BaO and SrO

2008 ◽  
Vol 1148 ◽  
Author(s):  
Chris E Mohn ◽  
Neil L. Allan ◽  
John H. Harding
Keyword(s):  
Density Functional Theory ◽  
Atomistic Simulation ◽  
Density Functional ◽  
Functional Theory ◽  
Bond Lengths ◽  
Simulation Techniques ◽  
Ultrathin Oxide Films ◽  
Anion Separation ◽  
Crystalline Oxides ◽  
Ultrathin Oxide

AbstractPrompted by renewed interest in the crystalline oxides-on-semiconductors interface, periodic density functional theory and atomistic simulation techniques are used to examine the formation of a layer of CaO on a BaO substrate. We examine how CaO islands which form at coverages less than 100% adjust to the substrate in which the cation-anion separation is substantially larger than in CaO itself. All Ca-O bond lengths in the island are shorter than that in bulk CaO. Corner O atoms in the islands are associated with particularly short Ca-O bond lengths, and the shape of the islands is dominated by (100) edges. Once formed, islands with intact edges will remain intact. Interactions between islands at larger coverages are also investigated and we see the formation of characteristic elliptical gaps and loops.

Nanoscale mapping of intrinsic defects in single-layer graphene using tip-enhanced Raman spectroscopy

2016 ◽  
Vol 52 (53) ◽  
pp. 8227-8230 ◽  
Author(s):  
Weitao Su ◽  
Naresh Kumar ◽  
Ning Dai ◽  
Debdulal Roy
Keyword(s):  
Raman Spectroscopy ◽  
Spatial Resolution ◽  
Single Layer ◽  
Single Layer Graphene ◽  
Intrinsic Defect ◽  
Intrinsic Defects ◽  
Layer Graphene ◽  
Tip Enhanced Raman Spectroscopy ◽  
20 Nm

Non-gap TERS with a contrast of 8.5 enables TERS mapping of graphene's intrinsic defect with a spatial resolution of 20 nm.

Insight into Elastic Properties of Binary Alkali Silicate Glasses; Prediction and Interpretation through Atomistic Simulation Techniques

2007 ◽  
Vol 19 (13) ◽  
pp. 3144-3154 ◽  
Author(s):  
Alfonso Pedone ◽  
Gianluca Malavasi ◽  
Alastair N. Cormack ◽  
Ulderico Segre ◽  
M. Cristina Menziani
Keyword(s):  
Elastic Properties ◽  
Atomistic Simulation ◽  
Silicate Glasses ◽  
Simulation Techniques ◽  
Alkali Silicate ◽  
Insight Into

Analysis of Oxygen Vacancy Trapping at [001] Symmetric Tilt Grain Boundaries in Barium Titanate by Atomistic Simulations

2010 ◽  
Vol 445 ◽  
pp. 39-42 ◽  
Author(s):  
Takashi Oyama ◽  
Nobuyuki Wada ◽  
Hiroshi Takagi
Keyword(s):  
Barium Titanate ◽  
Grain Boundaries ◽  
Atomistic Simulation ◽  
Oxygen Vacancies ◽  
Atomistic Simulations ◽  
Multilayer Ceramic Capacitors ◽  
Simulation Techniques ◽  
Electrical Degradation ◽  
Symmetric Tilt

The role of grain boundaries (GBs) in the diffusion of oxygen vacancies (VO••s) in barium titanate (BaTiO3) and its mechanism were investigated using atomistic simulation techniques. It was found that GBs trapped VO••s at specific sites in the course of the diffusion, and the excess energy reflecting structural distortion of the GB was closely related to the availability of the trapping. GBs therefore act as a resistance of the diffusion of VO••s, suggesting that electrical degradation of multilayer ceramic capacitors (MLCCs), which is derived from vacancy diffusion, enables to be additionally improved by controlling GB structures in BaTiO3-based dielectrics.

scholarly journals Atomistic simulation of CeO2 surface hydroxylation: implications for glass polishing

2008 ◽  
Vol 43 (12) ◽  
pp. 4157-4162 ◽  
Author(s):  
Christopher R. Stanek ◽  
Averyl H. H. Tan ◽  
Scott L. Owens ◽  
Robin W. Grimes
Keyword(s):  
Atomistic Simulation ◽  
Morphological Changes ◽  
Dissociative Adsorption ◽  
Atomistic Simulations ◽  
Surface Energies ◽  
Simulation Techniques ◽  
Surface Configuration ◽  
Adsorption Of Water ◽  
Surface Hydroxylation ◽  
Glass Polishing

AbstractAtomistic simulation techniques have been used to investigate the dissociative adsorption of water on the (110), (111), and (100) low index surfaces of CeO2, as well as a so-called “trench” surface configuration. Several different coverages of water have been considered to better understand how the hydroxylation process progresses. Hydroxylation energies and surface energies of CeO2 calculated via atomistic simulations are compared to similar results for other fluorite oxides. Finally, the modification of CeO2 crystallite morphology in the presence of water is predicted from the changes in surface energy and the implications of these morphological changes for glass polishing are discussed.

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