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Journal ArticleDOI

From ultrasoft pseudopotentials to the projector augmented-wave method

15 Jan 1999-Physical Review B (American Physical Society)-Vol. 59, Iss: 3, pp 1758-1775
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.
Citations
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Journal ArticleDOI
TL;DR: In this article, the authors report dimensionless thermoelectric properties of tetrahedrites, the most widespread sulfosalts on Earth, and further show that the natural mineral itself can be used directly as an inexpensive source of energy.
Abstract: Thermoelectric materials can convert waste heat into electricity, potentially improving the effi ciency of energy usage in both industry and everyday life. Unfortunately, known good thermoelectric materials often are comprised of elements that are in low abundance and require careful doping and complex synthesis procedures. Here, we report dimensionless thermoelectric fi gure of merit near unity in compounds of the form Cu 12 − x M x Sb 4 S 13 , where M is a transition metal such as Zn or Fe, for wide ranges of x . The compounds investigated here span the range of compositions of the natural mineral family of tetrahedrites, the most widespread sulfosalts on Earth, and we further show that the natural mineral itself can be used directly as an inexpensive source thermoelectric material. Thermoelectrics comprised of earth-abundant elements will pave the way to many new, low cost thermoelectric energy generation opportunities.

435 citations

Journal ArticleDOI
TL;DR: This work reports a system based on palladium icosahedra that demonstrates an effective approach to the development of electrocatalysts with greatly enhanced activity and durability.
Abstract: Core-shell catalysts can enhance activity while reducing the loading of expensive catalyst materials. Here, the authors report a palladium@platinum system in which the platinum shells evolve into a corrugated structure with compressive strains, with subsequent enhancement of oxygen reduction activity.

434 citations

Journal ArticleDOI
TL;DR: The authors reveal that the voltage of anion redox is strongly affected by structural changes that occur during battery cycling, explaining its unique electrochemical properties.
Abstract: Lithium-rich layered transition metal oxide positive electrodes offer access to anion redox at high potentials, thereby promising high energy densities for lithium-ion batteries. However, anion redox is also associated with several unfavorable electrochemical properties, such as open-circuit voltage hysteresis. Here we reveal that in Li1.17-x Ni0.21Co0.08Mn0.54O2, these properties arise from a strong coupling between anion redox and cation migration. We combine various X-ray spectroscopic, microscopic, and structural probes to show that partially reversible transition metal migration decreases the potential of the bulk oxygen redox couple by > 1 V, leading to a reordering in the anionic and cationic redox potentials during cycling. First principles calculations show that this is due to the drastic change in the local oxygen coordination environments associated with the transition metal migration. We propose that this mechanism is involved in stabilizing the oxygen redox couple, which we observe spectroscopically to persist for 500 charge/discharge cycles.

434 citations

Journal ArticleDOI
Abstract: MoSe2 grown on N,P-co-doped carbon nanosheets is synthesized by a solvothermal reaction followed with a high-temperature calcination. This composite has an interlayer spacing of MoSe2 expanded to facilitate sodium-ion diffusion, MoSe2 immobilized on carbon nanosheets to improve charge-transfer kinetics, and N and P incorporated into carbon to enhance its interaction with active species upon cycling. These features greatly improve the electrochemical performance of this composite, as compared to all the controls. It presents a specific capacity of 378 mAh g−1 after 1000 cycles at 0.5 A g−1, corresponding to 87% of the capacity at the second cycle. Ex situ Raman spectra and high-resolution transmission electron microscopy images confirm that it is element Se, rather than MoSe2, formed after the charging process. The interaction of the active species with modified carbon is simulated using density functional theory to explain this excellent stability. The superior rate capability, where the capacity at 15 A g−1 equals ≈55% of that at 0.5 A g−1, could be associated with the significant contribution of pseudocapacitance. By pairing with homemade Na3V2(PO4)3/C, this composite also exhibits excellent performances in full cells.

434 citations

Journal ArticleDOI
TL;DR: MnBi_{2}Te_{4} is the first stoichiometric material predicted to realize the zero plateau quantum anomalous Hall state intrinsically and has been theoretically shown to host the exotic axion insulator phase.
Abstract: Using density functional theory and Monte Carlo calculations, we study the thickness dependence of the magnetic and electronic properties of a van der Waals interlayer antiferromagnet in the two-dimensional limit. Considering ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ as a model material, we find it to demonstrate a remarkable set of thickness-dependent magnetic and topological transitions. While a single septuple layer block of ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ is a topologically trivial ferromagnet, the thicker films made of an odd (even) number of blocks are uncompensated (compensated) interlayer antiferromagnets, which show wide band gap quantum anomalous Hall (zero plateau quantum anomalous Hall) states. Thus, ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ is the first stoichiometric material predicted to realize the zero plateau quantum anomalous Hall state intrinsically. This state has been theoretically shown to host the exotic axion insulator phase.

433 citations

References
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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