From ultrasoft pseudopotentials to the projector augmented-wave method
TL;DR: In this paper, the formal relationship between US Vanderbilt-type pseudopotentials and Blochl's projector augmented wave (PAW) method is derived and the Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional.
Abstract: The formal relationship between ultrasoft (US) Vanderbilt-type pseudopotentials and Bl\"ochl's projector augmented wave (PAW) method is derived. It is shown that the total energy functional for US pseudopotentials can be obtained by linearization of two terms in a slightly modified PAW total energy functional. The Hamilton operator, the forces, and the stress tensor are derived for this modified PAW functional. A simple way to implement the PAW method in existing plane-wave codes supporting US pseudopotentials is pointed out. In addition, critical tests are presented to compare the accuracy and efficiency of the PAW and the US pseudopotential method with relaxed core all electron methods. These tests include small molecules $({\mathrm{H}}_{2}{,\mathrm{}\mathrm{H}}_{2}{\mathrm{O},\mathrm{}\mathrm{Li}}_{2}{,\mathrm{}\mathrm{N}}_{2}{,\mathrm{}\mathrm{F}}_{2}{,\mathrm{}\mathrm{BF}}_{3}{,\mathrm{}\mathrm{SiF}}_{4})$ and several bulk systems (diamond, Si, V, Li, Ca, ${\mathrm{CaF}}_{2},$ Fe, Co, Ni). Particular attention is paid to the bulk properties and magnetic energies of Fe, Co, and Ni.
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TL;DR: The strong synergism in the coadsorption of CO and O2 on the Au-Ag nanoparticle can thus explain the observed synergetic effect in catalysis.
Abstract: We report a novel Au−Ag alloy catalyst supported on mesoporous aluminosilicate Au−Ag@MCM prepared by a one-pot synthesis procedure, which is very active for low-temperature CO oxidation. The activity was highly dependent on the hydrogen pretreatment conditions. Reduction at 550−650 °C led to high activity at room temperature, whereas as-synthesized or calcined samples did not show any activity at the same temperature. Using various characterization techniques, such as XRD, UV−vis, XPS, and EXAFS, we elucidated the structure and surface composition change during calcination and the reduction process. The XRD patterns show that particle size increased only during the calcination process on those Ag-containing samples. XPS and EXAFS data demonstrate that calcination led to complete phase segregation of the Au−Ag alloy and the catalyst surface is greatly enriched with AgBr after the calcination process. However, subsequent reduction treatment removed Br- completely and the Au−Ag alloy was formed again. The su...
232 citations
TL;DR: The question of stability against diffusional mixing at the prototypical LaAlO3/SrTiO3(001) interface is explored using a multi-faceted experimental and theoretical approach as discussed by the authors.
232 citations
TL;DR: In this article, the authors report on an alternative class of phosphors, [(Y,Sc)(Nb,V)O4:Bi3+], which exhibit homogeneous Bi3+ luminescence.
Abstract: The use of rare-earth (RE) (e.g., Eu2+/Ce3+) ions as single luminescent centers in phosphors with tailorable emission properties has been extensively studied for their potential use in white LEDs. However, significant limitations remain, in particular, for red-emitting phosphors due to the inherently broad excitation bands which result from the underlying d–f transitions and span large parts of the visible spectral region. Guided by density functional theory calculations on the ligand structure of the non-RE Bi3+ ion, we report here on an alternative class of phosphors, [(Y,Sc)(Nb,V)O4:Bi3+], which exhibit homogeneous Bi3+ luminescence. In these materials, adjustment of the cation fractions enables dedicated tailoring of the excitation scheme within the spectral range of ∼340–420 nm and, in the meanwhile, allows for tunable emission spanning from about 450 nm (blue) to 647 nm (orange-red). The practical absence of any overlap between the emission and excitation spectra addresses the issues of emission col...
232 citations
TL;DR: In this paper, porous Fe2O3 nanospheres anchored on activated carbon cloth are used as an excellent electrode material, which exhibits a large area specific capacitance up to 2775mF cm−2 in 3´M LiNO3 between −0.8 and 0´V versus SCE.
232 citations
TL;DR: In this article, the optical properties of α and β allotropes of antimonene monolayers have been calculated within the random phase approximation (RPA) using density functional theory.
Abstract: Two-dimensional materials draw further attention because of their superior properties applicable in novel technologies. We have calculated the optical properties of α and β allotropes of antimonene monolayers. Their dielectric matrices have been calculated within the random phase approximation (RPA) using density functional theory. We have calculated dielectric functions, absorption coefficients, refractive indices, electron energy loss spectra and optical reflectivities in the energy range between 0 and 21 eV. Our simulations predict that absorption process starts in the infrared, but peaks in the ultraviolet region. The values of refractive index are 2.3 (α-Sb) and 1.5 (β-Sb) at the zero energy limit and scale up to 3.6 in the ultraviolet region. Reflection rises up to 86% at the UV energies, where antimonene behaves like a metal regarding the incident electromagnetic radiation. Our calculations show that antimonene is suitable as a material for the microelectronic and optoelectronic nanodevices and solar cell applications, as well as for new optical applications using various light emission, detection, modulation and manipulation functions.
231 citations
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Book•
31 Dec 1993
TL;DR: The linearized augmented planewave (LAPW) method has emerged as the standard by which density functional calculations for transition metal and rare-earth containing materials are judged.
Abstract: With its extreme accuracy and reasonable computational efficiency, the linearized augmented planewave (LAPW) method has emerged as the standard by which density functional calculations for transition metal and rare-earth containing materials are judged. This volume presents a thorough and self-conta
1,150 citations