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: Using photoelectron spectroscopy, the interface formation of anatase and rutile TiO2 with RuO2 and tin-doped indium oxide (ITO) is studied in this paper.
Abstract: Using photoelectron spectroscopy, the interface formation of anatase and rutile TiO2 with RuO2 and tin-doped indium oxide (ITO) is studied. It is consistently found that the valence band maximum of rutile is 0.7 ± 0.1 eV above that of anatase. The alignment is confirmed by electronic structure calculations, which further show that the alignment is related to the splitting of the energy bands formed by the O 2pz lone-pair orbitals. The alignment can explain the different electron concentrations in doped anatase and rutile and the enhanced photocatalytic activity of mixed phase particles.
217 citations
TL;DR: In this paper, the impurity diffusion coefficients of Mg, Si and Cu in dilute face-centered cubic Al alloys were predicted from first principles using density functional theory (DFT) calculations.
217 citations
TL;DR: Using the covalent triazine framework (CTF) as a representative, this article explored 2D organic semiconductors using first-principles calculations and identified the CTF as a new class of 2D visible-light-driven organocatalyst for water splitting.
Abstract: Since the graphene boom, great efforts have been devoted to two-dimensional (2D) monolayer materials with exciting possibilities for applications. Most known 2D materials are inorganic. Using the covalent triazine framework (CTF) as a representative, we explored 2D organic semiconductors using first-principles calculations. From a systematic study of the electronic band structures, work functions, CBM/VBM positions, and optical absorption spectra, we identified the CTF as a new class of 2D visible-light-driven organocatalyst for water splitting. Controllable construction of such CTFs from suitable organic subunits paves the way to correlate band alignment and chemical composites. In addition, multilayer CTFs have enhanced visible-light absorption compared to monolayer CTFs due to interlayer coupling. Our theoretical prediction not only has fulfilled the search for organic counterparts of inorganic photocatalysts for water splitting, but also would motivate scientists to further search for novel 2D organic materials with other technological applications.
217 citations
TL;DR: The low saturation field and the superlattice nature of MnBi4Te7 make it an ideal system to investigate rich emergent phenomena and an intrinsic natural heterostructural Z2 antiferromagnetic topological insulator with low out-of-plane saturation fields.
Abstract: Magnetic topological insulators (TI) provide an important material platform to explore quantum phenomena such as quantized anomalous Hall effect and Majorana modes, etc. Their successful material realization is thus essential for our fundamental understanding and potential technical revolutions. By realizing a bulk van der Waals material MnBi4Te7 with alternating septuple [MnBi2Te4] and quintuple [Bi2Te3] layers, we show that it is ferromagnetic in plane but antiferromagnetic along the c axis with an out-of-plane saturation field of ~0.22 T at 2 K. Our angle-resolved photoemission spectroscopy measurements and first-principles calculations further demonstrate that MnBi4Te7 is a Z2 antiferromagnetic TI with two types of surface states associated with the [MnBi2Te4] or [Bi2Te3] termination, respectively. Additionally, its superlattice nature may make various heterostructures of [MnBi2Te4] and [Bi2Te3] layers possible by exfoliation. Therefore, the low saturation field and the superlattice nature of MnBi4Te7 make it an ideal system to investigate rich emergent phenomena.
217 citations
TL;DR: In this paper, in situ CO IR spectroscopy and density functional theory (DFT) was used to establish that Pd/CeO2-rods are active due to a Langmuir-Hinshelwood mechanism involving isolated Pd atoms in the form of Pd 1O and Pd1O 2 species.
Abstract: Pd/CeO2 is an active component in emission control catalysts for CO oxidation. Nanostructured CeO2 powders can be prepared in the form of rods exposing predominantly (111) surfaces and cubes exposing (100) surfaces. While differences in the reactivity of Pd supported on these facets of ceria have been reported, the origins of the reactivity differences are not well understood. Pd supported on (111) surfaces of ceria rods exhibits room-temperature CO oxidation activity, while Pd on (100) surface of ceria cubes shows comparable activity at a temperature that is 60 °C higher. Earlier, we established that Pd/CeO2-rods are active due to a Langmuir-Hinshelwood mechanism involving isolated Pd atoms in the form of Pd1O and Pd1O2 species. Here, we establish using in situ CO IR spectroscopy and density functional theory (DFT) that, in addition to TEM-visible Pd nanoparticles, Pd/CeO2-cubes also contain isolated Pd species, predominantly in the form of Pd1O. DFT calculations show that CO oxidation proceeds via a Mars-van Krevelen pathway, which is possible for the (100) surface because of the lower Ce-O binding energy compared to the (111) surface. Overall, the catalytic cycle for CO oxidation on Pd/CeO2(100) involves a higher free energy barrier than on Pd/CeO2(111) in keeping with the experimentally observed activity difference. EXAFS measurements show that the active Pd phase in both Pd/CeO2-rods and Pd/CeO2-cubes responds dynamically with respect to reducing and oxidizing conditions. The redispersion of Pd in oxidative conditions is more pronounced for Pd/CeO2-rods and the catalyst is more active after an oxidative treatment.
217 citations
Cites methods from "From ultrasoft pseudopotentials to ..."
...The projector augmented wave (PAW) method [47,48] was used to describe the interaction between the ions and the electrons with the frozen-core approximation....
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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