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: In this article, a hierarchical porous graphene macrostructure coupled with uniformly distributed α-Fe2O3 nano-particles (denoted Fe-PGM) was designed as a sulfur host in a lithium-sulfur battery, and was prepared by a hydrothermal method.
327 citations
TL;DR: In this article, the conversion of furfural (FAL) and 2-methyl pentanal (MPAL) under hydrogen has been studied over silica-supported monometallic Pd and bimetallic pd-Cu catalysts.
327 citations
TL;DR: In this article, the density functional calculations for CO on Rh(111) indicate that the applied semilocal functionals clearly favor CO adsorption in the hollow site, which is in disagreement with experimental studies which all point towards atop adaption at low coverage.
Abstract: We present detailed density functional calculations for CO on Rh(111). At low coverage, the applied semilocal functionals clearly favor CO adsorption in the hollow site. This is in disagreement with experimental studies which all point towards atop adsorption at low coverage. The experimental assignment is confirmed by theoretical calculations of the vibrational frequencies and core level shifts at various coverages, ranging from $1∕9\phantom{\rule{0.5em}{0ex}}\text{to}\phantom{\rule{0.5em}{0ex}}3∕4$ $[(2\ifmmode\times\else\texttimes\fi{}2)\text{\ensuremath{-}}3\mathrm{C}\mathrm{O}]$ monolayer CO. For atop adsorption the calculated vibrational frequencies and the Rh surface core level shifts are indeed found to agree very well with experiment. To understand these controversial results, a molecular $\mathrm{GGA}+\mathrm{U}$ method is applied, which allows one to shift the CO $2\ensuremath{\pi}*$ orbital towards the vacuum level. This reduces the binding energy in the hollow site and brings the theoretical site preference in agreement with experiment. It is investigated how this molecular $\mathrm{GGA}+\mathrm{U}$ method influences the vibrational properties and the surface core level shifts. Furthermore, details on the molecular $\mathrm{GGA}+\mathrm{U}$ method are presented.
327 citations
TL;DR: Using atomistic simulations, it is revealed that the LCO of the multi-principal-element NiCoCr SS changes with alloy processing conditions, producing a wide range of generalized planar fault energies.
Abstract: High-entropy alloys (HEAs) were presumed to have a configurational entropy as high as that of an ideally mixed solid solution (SS) of multiple elements in near-equal proportions. However, enthalpic interactions inevitably render such chemically disordered SSs rare and metastable, except at very high temperatures. Here we highlight a structural feature that sets these concentrated SSs apart from traditional solvent-solute ones: the HEAs possess a wide variety of (local) chemical ordering (LCO). Our atomistic simulations employing an empirical interatomic potential for NiCoCr reveal that the LCO of the multi-principal-element SS changes conspicuously with alloy processing conditions, producing a wide range of generalized planar fault energy in terms of both its sample-average and spatial variation. We further demonstrate that the LCO heightens the ruggedness of the energy landscape and raises activation barriers governing dislocation activities. This not only influences the selection of dislocation pathways in slip, faulting, twinning, and martensitic transformation, but also increases the lattice friction to dislocation motion via a new mechanism of nanoscale segment detrapping that elevates the mechanical strength. All these open a vast playground not accessible to ground-state SSs or intermetallics, offering rich opportunities to tune properties.
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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