Papers by Keyword: First-Principle Calculations

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Authors: Li Wang, Jian Hong Gong, Jun Gao
Abstract: We employ density functional theory to investigate TiAl3/Al interfaces with the orientation of (001) [100]Al//(001)[100]TiAl3 by electronic structures, relaxed atomic geometries and adhesions. The preferable interfacial atomic structure is that wherein Al atoms continue on the natural stacking sequence of bulk TiAl3. Two types of TiAl3 (001) slabs, Ti-centered, all Al atoms, are adopted to compare interfacial energy, interfacial electronic structure. The calculated adhesion energies Wad of the two types of interface are very close, and are quantitatively in agreement with other calculated results of Al on the carbide and nitride, but much lower than the (111)Al[1 0]Al//(0001)TiB2[11 0]TiB2 adhesion energy. We have thoroughly characterized the electronic structure and determined that the metallic Al-3p and Ti-3d bonding constitute the primary interfacial bonding interaction.
Authors: Guido Roma
Abstract: The main task of the silicon carbide layer in Triso-coated fuel particles for gas-cooled high temperature fission reactors is to retain fission products. It has been observed that some fission products, and in particular Pd, attack the SiC layer and are supposed to be responsible for corrosion of the material, which could facilitate fission products release. We used first principles calculations based on Density Functional Theory (DFT) in order to investigate the energetic, structural, and kinetic properties of Pd impurities inside SiC; we obtained solution and migration energies in pure SiC and discuss the thermodynamics of a few reactions that could possibly occur for Pd impurities in silicon carbide.
Authors: Dong Xu Li, Jing Lu, Dong Li Yu
Abstract: Diamond with inorganic coating such as silicon coatings was used to promote applications. Different kinds of silicon structures were found in the coatings. In this paper, first principle calculation was used to study the stability of cubic silicon and hexagonal silicon coatings deposited on diamond substrate. The simulation data suggest that the single layer hexagonal silicon coating form easily under low temperature due to the low lattice mismatching and thermodynamic temperature. However, the stronger bonding of Si-C bonds between substrate and coating direct the formation of cubic silicon coatings, as well as Si-Si bonds inner coatings, in agreement with experiments.
Authors: In Gee Kim, Gul Rahman, Jae Hoon Jang, You Young Song, Seung Woo Seo, H.K.D.H. Bhadeshia, A.J. Freeman, G.B. Olson
Abstract: The formation enthalpy of a series of Fe-C carbides has been estimated using a first-principles approach. The Fe to C ratio dependence of the formation enthalpy is reasonable, but it is revealed that - and -carbides require an extraordinary environment to be able to form. Furthermore, an addition of substitutional solutes other than Fe and C should promote other carbides with different crystal structures. The analysis suggests further studies to discover the critical concentrations of alloying which stimulate the other carbides to become more stable.
Authors: Kefren Sánchez, Irene Aguilera, Pablo Palacios, Perla Wahnón
Abstract: First-principles calculations carried out for compounds based on Si implanted with different species, as Ti or chalcogens (S, Se, Te), show them as solid candidates to intermediate band (IB) photovoltaic materials. This DFT study predicts electronic structures, formation energies, relaxed atomic structures, optoelectronic properties, diffusion paths, for supercells containing up to several hundreds of atoms. The knowledge of Si-based devices is a relevant factor to facilitate the creation of an IB solar cell. Crystalline samples with a concentration of Ti several orders of magnitude above the solubility limit have been already grown. Formation energy calculations agree with the experiment in showing mainly interstitial implantation. Calculated electronic structure presents an IB, which is in agreement with electrical measurements and models, and is expected to cause an increase of the absorption coefficient across the solar spectrum. Chalcogen-implanted Si is an efficient IR absorber when implantation is carried out at ultra-high concentrations. Substitutional implantation produces a filled band inside Si band-gap and our calculations predict that plausible co-doping with IIIA atoms (as Al, B) would allow to obtain an IB fulfilling all the needed requirements.
Authors: Jaroslaw Dąbrowski, Hans Joachim Müssig, G. Wolff, Waleran Arabczyk, S. Hinrich
Authors: Atsushi Honda, Shin'ichi Higai, Takafumi Okamoto, Noriyuki Inoue, Yasuhiro Motoyoshi, Nobuyuki Wada, Hiroshi Takagi
Abstract: We performed first-principles calculations to examine the interaction among rare-earth (RE), alkaline-earth (AE) elements and oxygen vacancy (VO) in BaTiO3, in order to clarify the combined effects of VO trapping by two different elements. It was found that there is a synergistic effect of VO trapping by RE at Ba site and AE at Ti site, so that the co-doping is effective to improve insulating reliability of BaTiO3. We also verified that the local atomic structures around dopants obtained by calculations well agree with that obtained experimentally by extended X-ray absorption fine structure (EXAFS) analyses. The present work is the first one to clarify the structural environment around dopants including VO by both theoretical and experimental approaches.
Authors: Hisaomi Iwata, Sven Öberg, Patrick R. Briddon
Authors: A. Zywietz, P. Käckell, J. Furthmüller, Friedhelm Bechstedt
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