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, the thickness-ultrathin and bismuth-rich strategies were ingenuously combined to enhance the photocatalytic performance of a photocatalyst via a glycerol precursor route.
Abstract: Two dimension layered BiOX (X = Cl, Br, I) semiconductor nanomaterials are very important photocatalysts. Our previous work showed that thickness-ultrathin and bismuth-rich strategies are excellent methods to improve the visible-light-driven (VLD) photocatalytic reduction activity of BiOX. In this study, thickness-ultrathin and bismuth-rich strategies were ingenuously combined to enhance the photocatalytic performance of the photocatalyst, via a glycerol precursor route, Bi 4 O 5 Br 2 microsphere assembled by ultrathin nanosheets was synthesized and characterized by X-ray diffraction (XRD) patterns, X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), high-resolution transmission electron microscopy (HRTEM), time-resolved PL spectra and UV–vis diffuse reflectance spectra (DRS). The thickness of Bi 4 O 5 Br 2 ultrathin nanosheets was about 3.7 nm, which was much thinner than the common BiOBr nanosheets (65 nm). Due to the thickness-ultrathin and bismuth-rich strategies, the synthesized Bi 4 O 5 Br 2 sample displayed a higher photocatalytic reduction activity of CO 2 conversion than BiOBr and ultrathin BiOBr under visible-light irradiation. More importantly, we found that thickness-ultrathin and bismuth-rich strategies played different roles. Thickness-ultrathin strategy only can increase the CO generation while bismuth-rich strategy only can increase the CH 4 generation for photoreduction of CO 2 .
271 citations
TL;DR: In this paper, a combination of state-of-the-art computational modeling and Fourier transform infrared (FTIR) spectroscopy study of the surface species formed during interaction of CO2 or CO with activated (stoichiometric), reduced, and hydroxylated ceria, CeO2, assigned various experimentally observed vibrational modes to individual types of surface species.
Abstract: Using a combination of state-of-the-art computational modeling and Fourier transform infrared (FTIR) spectroscopy study of the surface species formed during interaction of CO2 or CO with activated (stoichiometric), reduced, and hydroxylated ceria, CeO2, we assigned various experimentally observed vibrational modes to individual types of surface species. We considered carbonates CO32–, formates HCO2–, and hydrogen carbonates CO2(OH)− bound in various ways to the surface of a ceria nanoparticle. Since the structure of the surface carbonate species is particularly versatile, we introduced a notation of different types of such species and computationally determined the regions where the characteristic vibrational frequencies of each type of species can be found. The complementary FTIR measurements of the surface species produced under different conditions revealed the actual experimental vibrational peaks and allowed estimation of the accuracy of the computational method to reproduce the frequencies of differ...
271 citations
TL;DR: A multicomponent FeCoCrNi alloy with dynamically formed Ni4+ species to offer high catalytic activity via lattice oxygen activation mechanism to offer highly intrinsic activity at low applied potentials is reported.
Abstract: Anodic oxygen evolution reaction (OER) is recognized as kinetic bottleneck in water electrolysis. Transition metal sites with high valence states can accelerate the reaction kinetics to offer highly intrinsic activity, but suffer from thermodynamic formation barrier. Here, we show subtle engineering of highly oxidized Ni4+ species in surface reconstructed (oxy)hydroxides on multicomponent FeCoCrNi alloy film through interatomically electronic interplay. Our spectroscopic investigations with theoretical studies uncover that Fe component enables the formation of Ni4+ species, which is energetically favored by the multistep evolution of Ni2+→Ni3+→Ni4+. The dynamically constructed Ni4+ species drives holes into oxygen ligands to facilitate intramolecular oxygen coupling, triggering lattice oxygen activation to form Fe-Ni dual-sites as ultimate catalytic center with highly intrinsic activity. As a result, the surface reconstructed FeCoCrNi OER catalyst delivers outstanding mass activity and turnover frequency of 3601 A gmetal−1 and 0.483 s−1 at an overpotential of 300 mV in alkaline electrolyte, respectively. Electrocatalytic water oxidation is facilitated by high valence states, but these are challenging to achieve at low applied potentials. Here, authors report a multicomponent FeCoCrNi alloy with dynamically formed Ni4+ species to offer high catalytic activity via lattice oxygen activation mechanism.
270 citations
TL;DR: In this paper, the electronic properties and Li storage capability of V2C and its corresponding fluoride and hydroxide were investigated and first-principles calculations were performed to study the electronic property and storage capability.
Abstract: First-principles calculations are performed to study the electronic properties and Li storage capability of V2C and its corresponding fluoride and hydroxide. We find that the V2C monolayer is metallic with antiferromagnetic configuration, while its derived V2CF2 and V2C(OH)2 in their the most stable configurations are small-gap antiferromagnetic semiconductors. Li adsorption could enhance the electric conductivity of V2C fluoride and hydroxide. The bare V2C monolayer shows fast Li diffusion with low diffusion barrier height and very high Li storage capacity (with theoretical value ∼940 mAh/g), while the passivated F or OH atoms on its surface tend to impede Li diffusion and largely reduce the Li storage capacity. Moreover, the average intercalation potentials for V2C-based materials are calculated to be relatively low. Our results suggest that V2C monolayer could be a promising anode material for Li-ion batteries.
270 citations
TL;DR: In this paper, the authors exploit the electronic structure underpinning of classic Cu[In,Ga]Se2 (CIGS) chalcopyrite solar absorbers to design Pb-free halide perovskites by transmuting 2Pb to the pair [BIB + CIII] such as [Cu + Ga] or [Ag + In] and combinations thereof.
Abstract: The long-term chemical instability and the presence of toxic Pb in otherwise stellar solar absorber APbX3 made of organic molecules on the A site and halogens for X have hindered their large-scale commercialization. Previously explored ways to achieve Pb-free halide perovskites involved replacing Pb2+ with other similar M2+ cations in ns2 electron configuration, e.g., Sn2+ or by Bi3+ (plus Ag+), but unfortunately this showed either poor stability (M = Sn) or weakly absorbing oversized indirect gaps (M = Bi), prompting concerns that perhaps stability and good optoelectronic properties might be contraindicated. Herein, we exploit the electronic structure underpinning of classic Cu[In,Ga]Se2 (CIGS) chalcopyrite solar absorbers to design Pb-free halide perovskites by transmuting 2Pb to the pair [BIB + CIII] such as [Cu + Ga] or [Ag + In] and combinations thereof. The resulting group of double perovskites with formula A2BCX6 (A = K, Rb, Cs; B = Cu, Ag; C = Ga, In; X = Cl, Br, I) benefits from the ionic, yet na...
270 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