Article
Crystallography
Lingling Xuan, Thierry Duffar
Summary: The proposed model explains the conversion mechanism between Ti3+ and Ti4+ during Ti:sapphire crystal growth process by considering the release of O-2 from the crystal surface consuming aluminum vacancies. A set of mass balance differential equations is established to describe the diffusion and chemical reaction processes. The preliminary numerical simulation using COMSOL Multiphysics (R) software shows qualitative agreement with experimental results, indicating the potential of the model for further studying point defect reactions during crystal growth of ionic crystals.
JOURNAL OF CRYSTAL GROWTH
(2021)
Article
Physics, Multidisciplinary
Hebatalla Elnaggar, Silvester Graas, Sara Lafuerza, Blanka Detlefs, Wojciech Tabis, Mateusz A. Gala, Ahmed Ismail, Ad van der Eerden, Marcin Sikora, Jurgen M. Honig, P. Glatzel, Frank de Groot
Summary: The study reveals that heating magnetite results in spontaneous charge reordering and a hole self-doping effect, with core-level x-ray spectroscopy measurements combined with theory uncovering three regimes of self-doping. These regimes map the temperature dependence of the electrical conductivity and magnetism up to the Curie temperature.
PHYSICAL REVIEW LETTERS
(2021)
Article
Chemistry, Multidisciplinary
Hanhwi Jang, Michael Y. Toriyama, Stanley Abbey, Brakowaa Frimpong, James P. Male, G. Jeffrey Snyder, Yeon Sik Jung, Min-Wook Oh
Summary: This study investigates the effect of cation disordering on electronic properties in multinary cubic compounds. Using density functional theory calculations and in situ Raman spectroscopy, it is demonstrated that Bi-Ag charged antisite defects facilitate cation disordering and act as principal donor defects controlling the electronic properties.
ADVANCED MATERIALS
(2022)
Article
Chemistry, Physical
Shivani Srivastava, Blas Pedro Uberuaga, Mark Asta
Summary: Density functional theory is used to investigate the effects of different local arrangements of Fe2+ and Fe3+ cations on oxygen vacancies in magnetite. The results show that the preferred defect configurations depend on the presence of nearest-neighbor Fe3+ cations. The lowest-energy defect formation energies vary by about 0.2 eV with the local environment and can further differ by approximately 1.1 eV depending on the spin configuration. The findings also have implications for oxygen transport.
JOURNAL OF PHYSICAL CHEMISTRY C
(2023)
Article
Chemistry, Physical
Swen Zerebecki, Soma Salamon, Joachim Landers, Yuke Yang, Yujin Tong, Eko Budiyanto, Daniel Waffel, Maik Dreyer, Sascha Saddeler, Tim Kox, Stephane Kenmoe, Eckhard Spohr, Stephan Schulz, Malte Behrens, Martin Muhler, Harun Tueysuez, R. Kramer Campen, Heiko Wende, Sven Reichenberger, Stephan Barcikowski
Summary: This study investigates the effects of cation occupancy on oxidation catalysis by utilizing pulsed laser defect engineering. By gradually altering the cation occupancy and studying its impact on the oxidation reaction of cinnamyl alcohol, the importance of octahedral Co3+ sites and the feasibility of pulsed laser processing in changing cation occupancy and crystallographic defect density are demonstrated.
Article
Crystallography
Andrejs Sabanskis, Matiss Plate, Andreas Sattler, Alfred Miller, Janis Virbulis
Summary: The prediction and adjustment of point defect distribution in silicon crystals is crucial for microelectronic applications. Simulation of growth processes using different point defect parameter sets is found to be effective, with models considering the impact of thermal stress showing the best agreement in the whole crystal.
Review
Materials Science, Ceramics
N. A. Masmali, Z. Osman, A. K. Arof
Summary: The article discusses the properties and applications of zinc-based two-cation oxide spinel semiconductors, highlighting their unique optical and electrical characteristics, ability to undergo multiple redox reactions, and magnetic properties.
CERAMICS INTERNATIONAL
(2021)
Article
Chemistry, Physical
Takuto Ushiro, Tatsuya Yokoi, Yusuke Noda, Eiji Kamiyama, Masato Ohbitsu, Hiroki Nagakura, Koji Sueoka, Katsuyuki Matsunaga
Summary: An artificial-neural-network (ANN) interatomic potential trained with data from density-functional-theory (DFT) calculations is developed to reveal favorable modes of large-sized vacancy clusters in silicon. The ANN potential reasonably predicts E-f values and relaxed structures obtained from DFT calculations for all modes examined, indicating better transferability compared to commonly used empirical potentials.
JOURNAL OF PHYSICAL CHEMISTRY C
(2021)
Article
Nanoscience & Nanotechnology
Masato Ohbitsu, Tatsuya Yokoi, Yusuke Noda, Eiji Kamiyama, Takuto Ushiro, Hiroki Nagakura, Koji Sueoka, Katsuyuki Matsunaga
Summary: The energetics of extended interstitial defects in crystalline Si were studied using an artificial-neural-network potential trained with density-functional-theory data. Formation energies were accurately calculated for different defect types, and their stability was found to depend on the number of interstitials. The simulation cell size was found to strongly influence the results. The ANN potential outperformed empirical potentials in predicting energies and defect structures. Fitting the ANN values to analytic functions can improve macroscopic simulations for device manufacturing processes.
SCRIPTA MATERIALIA
(2022)
Article
Nanoscience & Nanotechnology
Ymir K. Frodason, Patryk P. Krzyzaniak, Lasse Vines, Joel B. Varley, Chris G. Van de Walle, Klaus Magnus H. Johansen
Summary: The diffusion of the n-type dopant Sn in beta-Ga2O3 was studied using secondary-ion mass spectrometry combined with hybrid functional calculations. It was found that Ga vacancies mediate the migration of Sn through the formation and dissociation of intermittent mobile VGaSnGa complexes. The migration barrier for the VGaSnGa complex was determined to be 3.0 +/- 0.4 eV, consistent with theoretical predictions using the nudged elastic band method.
Article
Physics, Applied
Haruo Sudo, Kozo Nakamura, Hideyuki Okamura, Susumu Maeda, Koji Sueoka
Summary: In this study, the formation behavior of oxygen precipitates in Si wafers after rapid thermal process was investigated through experiments and simulations. The oxygen precipitate density was found to vary based on the temperature and duration of the two-step heat treatment. The simulation effectively reproduced the variations in the oxygen precipitate densities, and indicated that the resulting density is determined by the nucleation rate, growth size, and timing of the terminal point of nucleation.
JOURNAL OF APPLIED PHYSICS
(2022)
Review
Materials Science, Multidisciplinary
Mark Jolly, Laurens Katgerman
Summary: Over the last four decades, significant progress has been made in the modelling of casting processes, enabling a better understanding of physical phenomena and calculation of difficult-to-measure quantities. However, there is still room for improvement in accurately predicting casting performance and defects.
PROGRESS IN MATERIALS SCIENCE
(2022)
Article
Chemistry, Multidisciplinary
Nusrat Jahan, M. N. I. Khan, M. R. Hasan, M. S. Bashar, A. Islam, M. K. Alam, M. A. Hakim, J. I. Khandaker
Summary: This study investigates the structural, electrical, and magnetic properties of diamagnetic aluminium substituted nickel-zinc-cobalt mixed spinel ferrites. The synthesized ferrite samples exhibit single-phase cubic spinel structures and highly resistive behavior, making them promising for high-frequency electronic devices.
Article
Chemistry, Physical
Luis Perez-Mas, Maria del Mar Ramos-Tejada, Alberto Martin-Molina, Jose-Alberto Maroto-Centeno, Manuel Quesada-Perez
Summary: In this study, we use coarse-grained simulations to investigate how electrostatic forces affect the diffusion of solute in flexible gels. The model considers the movement of solute particles and polyelectrolyte chains and uses a Brownian dynamics algorithm. We analyze the impact of three electrostatic parameters on the system. Our findings reveal that changes in the electric charge of the species influence both the diffusion coefficient and the anomalous diffusion exponent. We also observe differences in the diffusion coefficient between flexible and rigid gels, particularly at low ionic strength. Additionally, the flexibility of the chains significantly affects the exponent of anomalous diffusion, even at high ionic strength (100 mM). Our simulations demonstrate that altering the charge of the polyelectrolyte chains does not have the same effect as changing the charge of the solute particles.
JOURNAL OF CHEMICAL PHYSICS
(2023)
Article
Chemistry, Physical
J. Ibanez-Perez, M. L. No, M. Oehring, H. Clemens, J. M. San Juan
Summary: This study demonstrates the hindering effect of Nb on the diffusion of Ti atoms in the α(2)-Ti3Al phase through mechanical spectroscopy measurements, with the activation energy increasing with Nb content. The mechanism of next-neighbor interaction of Nb atoms with the local configuration of Ti-V-Ti is proposed to explain the observed experimental behavior, leading to a further broadening of the relaxation peak.
JOURNAL OF ALLOYS AND COMPOUNDS
(2021)
Article
Materials Science, Multidisciplinary
Christopher N. Singh, Blas Pedro Uberuaga, Stephen J. Tobin, Xiang-Yang Liu
Summary: The relative rate of optical to thermal carrier decay is crucial for optoelectronic device performance, and radiation-induced point defects have a significant impact on this ratio. By employing a first-principles-based theory of multi-phonon emission, the thermal decay rates of six possible point defects in GaAs, a classical optoelectronic material, are evaluated. These rates reveal the propensity of electrons or holes to interact with specific defect vibrations, shedding light on the most detrimental material defects.
Article
Chemistry, Physical
Florian Bocchese, Iain Brown, David Cornil, Pavel Moskovkin, Jerome Muller, Steven David Kenny, Roger Smith, Stephane Lucas
Summary: This study investigates the growth process and properties of Ag films on ZnO using magnetron sputtering through thin film growth simulations. A new method to account for defects generated by magnetron sputtering has been developed. The simulated conductivity matches experimental results with the difference attributed to electron scattering at grain boundaries. The study also shows that a patterned substrate does not increase conductivity but leads to controlled growth of small islands suitable for other applications.
APPLIED SURFACE SCIENCE
(2023)
Article
Physics, Condensed Matter
Peter Hatton, Michael Watts, Ying Zhou, Roger Smith, Pooja Goddard
Summary: The doping of CdTe with As is a promising method for increasing cell efficiency. Calculations using Density Functional Theory show that isolated As atoms can diffuse easily in bulk CdTe, indicating unhindered transport. However, substitutional arsenic in bulk CdTe has little effect on the band gap. In contrast, arsenic in grain boundaries introduces defect states into the band gap, suggesting a doping strategy involving chlorine saturation before introducing arsenic atoms.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2023)
Review
Materials Science, Multidisciplinary
Mitra L. Taheri, William Carter, Blas Pedro Uberuaga
Summary: This article discusses the demands placed on materials by coupled extreme environments and introduces new materials science methods and opportunities to facilitate research and design of new materials.
Article
Chemistry, Physical
Peter Hatton, Blas Pedro Uberuaga
Summary: In this study, it is found that highly disordered spinels with high concentration of antisite cation pairs still exhibit some short range order in the form of antisite chains. The formation of these chains depends on the chemistry of spinels. The effect of antisite chains on cation vacancy diffusivity varies depending on the spinel chemistry.
JOURNAL OF MATERIALS CHEMISTRY A
(2023)
Article
Materials Science, Multidisciplinary
Sylvia Koerfer, Alexander Bonkowski, Joe Kler, Peter Hatton, Blas Pedro Uberuaga, Roger A. De Souza
Summary: In this study, cation diffusion in fluorite-structured CeO2 is investigated using classical molecular dynamics and metadynamics simulations. It is found that cation diffusion primarily occurs through cation divacancies, rather than isolated vacancies or cation vacancy-oxygen vacancy associates.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Physics, Applied
R. Auguste, M. O. Liedke, M. Butterling, B. P. Uberuaga, F. A. Selim, A. Wagner, P. Hosemann
Summary: Radiation-induced property changes in materials are caused by energy transfer from incoming particles to the lattice, leading to atom displacement and the formation of extended defects. The extent of these defects depends on dose rate, material, and temperature. This study provides direct experimental evidence of non-equilibrium vacancy formation in silicon through in situ positron annihilation spectroscopy.
JOURNAL OF APPLIED PHYSICS
(2023)
Article
Materials Science, Coatings & Films
Sofia K. Pinzon, James A. Valdez, Vancho Kocevski, J. K. Baldwin, Blas P. Uberuaga, Cortney R. Kreller, Benjamin K. Derby
Summary: The study analyzes the effect of different substrate temperatures and altering the oxide cation on the structural and morphological properties of lanthanide sesquioxide thin films. It was found that the structure and morphology of the films can be controlled by manipulating deposition parameters.
JOURNAL OF VACUUM SCIENCE & TECHNOLOGY A
(2023)
Article
Materials Science, Multidisciplinary
Christopher N. Singh, Xiang-Yang Liu, Blas Pedro Uberuaga, Stephen J. Tobin
Summary: There is growing demand for radiation-tolerant optical systems in space and nuclear applications. This study utilizes advanced modeling techniques to design radiation-hard optical materials. Molecular dynamics, density functional theory, and Maxwell's equations were used to analyze the effects of point-defects on radiation-induced attenuation in wet fused silica. Evidence is provided that non-bridging oxygen-hole centers (NBOHC) are the primary cause of attenuation in γ-irradiated optical fibers. The study also highlights the importance of spin-orbit coupling in defining the optical properties of gamma-ray induced defects.
MATERIALS TODAY COMMUNICATIONS
(2023)
Article
Chemistry, Physical
Amitava Banerjee, Edward F. Holby, Aaron A. Kohnert, Shivani Srivastava, Mark Asta, Blas P. Uberuaga
Summary: This study investigates the thermodynamics and kinetics of point defects in hematite (α-Fe2O3) using density functional theory. The calculations reveal that migration barriers for point defects can vary significantly with charge state, especially for cation interstitials. Multiple possible migration pathways are found, attributed to the low symmetry of the corundum crystal structure. Additionally, the anisotropy of long-range diffusion favors diffusion along the c-axis of the crystal.
ELECTRONIC STRUCTURE
(2023)
Article
Materials Science, Multidisciplinary
Anjana Talapatra, Blas Pedro Uberuaga, Christopher Richard Stanek, Ghanshyam Pilania
Summary: The compositional and structural variety of oxide perovskites allows for a wide range of applications. Machine learning models are used to predict the band gap of perovskite compounds and identify stable and synthesizable compounds with desired band gaps.
COMMUNICATIONS MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
V. Kocevski, J. A. Valdez, B. K. Derby, Y. Q. Wang, G. Pilania, B. P. Uberuaga
Summary: Introduces the importance of metastable forms of matter in our everyday lives, and explains that synthesizing these forms is more of an art than a science. Calculates metastable phase diagrams and extracts the metastability threshold to aid in their fabrication. Uses lanthanide sesquioxides (Ln(2)O(3)) as a case study to demonstrate the insight provided by metastable phase diagrams and predict the sequence of metastable phases induced by irradiation in Lu2O3.
MATERIALS ADVANCES
(2023)
Article
Materials Science, Multidisciplinary
David A. Andersson, Christopher R. Stanek, Christopher Matthews, Blas P. Uberuaga
Summary: This article introduces the motivation of new reactor concepts in studying various types of nuclear fuels. It discusses the types, properties, and historical context of the most prevalent nuclear fuels, as well as provides a perspective on the future development of nuclear fuel research. The author believes that the integration of modeling and simulation with experiments will be crucial in extracting the maximum amount of energy from existing fuels in a safe and economical way.
Article
Chemistry, Physical
Vancho Kocevski, Ghanshyam Pilania, Blas P. Uberuaga
Summary: Complex oxides exhibit great functionality due to their varied chemistry and structures. This study introduces a simple metric that correlates the propensity for cation disordering in perovskites, pyrochlores, and spinels with the energy to invert the cation structure. The metric provides a fast and robust way to determine the ease or difficulty of cation disordering, enabling quick screening of compounds for cation-ordering-dependent functionalities.
PHYSICAL CHEMISTRY CHEMICAL PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Ying Zhou, Prashanth Srinivasan, Fritz Kormann, Blazej Grabowski, Roger Smith, Pooja Goddard, Andrew Ian Duff
Summary: Multi-principal-component alloys, such as high entropy alloys (HEAs), have unique properties and a vast compositional space, making them attractive for alloy design. This study focuses on using computational materials design to investigate the high-temperature properties of HEAs, specifically the full free energy surface and thermodynamic properties. The developed approach, based on density-functional theory and machine learning, shows a significant speed-up and accurate predictions of high-temperature free energy. The study is performed on an equiatomic HEA composition, which may have potential applications in next generation fission and fusion reactors.
