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 deposition of Cu and Au nanoparticles on TiO2(110) produces very good catalysts for the WGS as discussed by the authors, and the catalysts that have the highest activity for WGS have also the lowest apparent activation energy.
Abstract: The deposition of Cu and Au nanoparticles on TiO2(110) produces very good catalysts for the WGS. Although bulk metallic gold is not active as a WGS catalyst, Au nanoparticles supported on TiO2(110) have an activity comparable to that of Cu/ZnO(000i). Cu/TiO2(110) is clearly a better catalyst than Cu/ZnO(0001) or Au/TiO2(110). The catalysts that have the highest activity for the WGS have also the lowest apparent activation energy. On Cu(111) and Cu(100), the aparent activation energies are 18.1 and 15.2 kcal/mol, respectively. The apparent activation energy decreases to 12.4 kcal/mol on Cu/ZnO(0001), 10.2 on Au/TiO2(110), and 8.3 kcal/mol on Cu/TiO2(110). The Cu ↔ titania interactions are substantially stronger than the Au ↔ titania interactions. This has an effect on the growth mode of the metals on TiO2(110). In images of scanning tunneling miscroscopy, the average particle size in Cu/TiO2(110) is smaller than that in Au/TiO2(110). The Cu particles are dispersed on the terraces and steps of the oxide ...
224 citations
TL;DR: A topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating.
Abstract: As an alternative technology to energy intensive distillations, adsorptive separation by porous solids offers lower energy cost and higher efficiency. Herein we report a topology-directed design and synthesis of a series of Zr-based metal-organic frameworks with optimized pore structure for efficient separation of C6 alkane isomers, a critical step in the petroleum refining process to produce gasoline with high octane rating. Zr6O4(OH)4(bptc)3 adsorbs a large amount of n-hexane but excluding branched isomers. The n-hexane uptake is ~70% higher than that of a benchmark adsorbent, zeolite-5A. A derivative structure, Zr6O4(OH)8(H2O)4(abtc)2, is capable of discriminating all three C6 isomers and yielding a high separation factor for 3-methylpentane over 2,3-dimethylbutane. This property is critical for producing gasoline with further improved quality. Multicomponent breakthrough experiments provide a quantitative measure of the capability of these materials for separation of C6 alkane isomers. A detailed structural analysis reveals the unique topology, connectivity and relationship of these compounds.
224 citations
TL;DR: A highly efficient, stable NiAu catalyst that exhibits unprecedented low temperature activity in lignin hydrogenolysis was developed in this paper, leading to the formation of 14 wt% aromatic monomers from organosolv Lignin at 170 °C in pure water.
224 citations
TL;DR: It is reported that the higher catalytic activity at the relatively low temperature results from the integration of nickel cations, cobalt cations and surface lattice oxygen atoms/oxygen vacancies at the atomic scale.
Abstract: It is crucial to develop a catalyst made of earth-abundant elements highly active for a complete oxidation of methane at a relatively low temperature NiCo2O4 consisting of earth-abundant elements which can completely oxidize methane in the temperature range of 350-550 °C Being a cost-effective catalyst, NiCo2O4 exhibits activity higher than precious-metal-based catalysts Here we report that the higher catalytic activity at the relatively low temperature results from the integration of nickel cations, cobalt cations and surface lattice oxygen atoms/oxygen vacancies at the atomic scale In situ studies of complete oxidation of methane on NiCo2O4 and theoretical simulations show that methane dissociates to methyl on nickel cations and then couple with surface lattice oxygen atoms to form -CH3O with a following dehydrogenation to -CH2O; a following oxidative dehydrogenation forms CHO; CHO is transformed to product molecules through two different sub-pathways including dehydrogenation of OCHO and CO oxidation
224 citations
TL;DR: It was theoretically demonstrated that a p-type graphene can be obtained via charge transfer between an organic molecule and graphene, and both the carrier concentration and band gap at the Dirac point can be controlled by coverage of organic molecules.
Abstract: The electronic structure of an electron-acceptor molecule, tetracyanoethylene (TCNE), on graphene was investigated using the first-principles method based on density functional theory. It was theoretically demonstrated that a p-type graphene can be obtained via charge transfer between an organic molecule and graphene. Both the carrier concentration and band gap at the Dirac point can be controlled by coverage of organic molecules. The spin split and partially filled π* orbitals of the TCNE anion radical induce spin density in the graphene layer. Surface modification of graphene by organic molecules could be a simple and effective method to control the electronic structure of graphene over a wide range.
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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