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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 paper, first-principles calculations were performed for silicene on two kinds of representative inert substrates, that is, hexagonal boron nitride (h-BN) monolayer and SiC(0001) surface.
Abstract: Silicene, a two-dimensional hexagonal lattice of silicon, has been synthesized recently and exhibits fascinating electronic properties that resemble graphene. The substrate effect on the electronic properties of silicene is important for the practical applications of silicene. First-principles calculations were performed for silicene on two kinds of representative inert substrates, that is, hexagonal boron nitride (h-BN) monolayer and SiC(0001) surface. The silicene–substrate interaction energies range in 0.067–0.089 eV per Si atom, belonging to typical van der Waals interaction. The characteristic Dirac cone is preserved for silicene on h-BN monolayer or hydrogenated Si-terminated SiC(0001) surface. On the other hand, the silicene becomes metallic when it is placed on a hydrogenated C-terminated SiC(0001) surface. This effect was explained by the work functions for silicene and the substrates. The present results provide some guidelines for selecting proper substrates for silicene in future microelectron...

246 citations

Journal ArticleDOI
TL;DR: In this article, the authors proposed a deoxygenation path that starts with the tautomerization of m-cresol to an unstable ketone intermediate (3-methyl-3,5-cyclohexadienone).
Abstract: The catalytic conversion of m-cresol in the presence of H2 has been investigated on SiO2-supported Ni, Fe, and bimetallic Ni–Fe catalysts at 300 °C and atmospheric pressure. Over the monometallic Ni catalyst, the dominant product is 3-methylcyclohexanone while 3-methylcyclohexanol and toluene appear in smaller amounts, even at high conversions. By contrast, on Fe and Ni–Fe bimetallic catalysts, the dominant product is toluene while the hydrogenation products (3-methylcyclohexanone and 3-methylcyclohexanol) are practically negligible in the entire range of conversions. To explain these differences, we have proposed a deoxygenation path that starts with the tautomerization of m-cresol to an unstable ketone intermediate (3-methyl-3,5-cyclohexadienone). The fate of this intermediate is determined by the ability of the catalyst to either hydrogenate the carbonyl group or the ring. The former would mostly occur on Fe and Ni–Fe catalysts that contain an oxophilic metal (Fe), while the latter would occur on Ni, which has a higher affinity for the aromatic ring. Hydrogenation of the carbonyl group produces a very reactive unsaturated alcohol (3-methyl-3,5-cyclohexadienol), which can be easily dehydrated to toluene. This would explain the high selectivity of Fe and Ni–Fe to toluene. By contrast, hydrogenation of the ring would result in 3-methylcyclohexanone, which can be further hydrogenated to 3-methylcyclohexanol. On supports that contain acid sites, which are active for dehydration, the formation of toluene would occur via dehydration of the alcohol and subsequent dehydrogenation. On the catalysts investigated in this work, dehydration of the corresponding alcohol does not occur, so the only path to toluene is via hydrogenation of the carbonyl of the unstable ketone intermediate. In addition, to the products mentioned above, xylenol is also observed in significant yields, which indicate that transalkylation of m-cresol is another reaction path occurring on these catalysts.

246 citations

Journal ArticleDOI
TL;DR: In this article, the interaction of dislocations with interfaces in a model Cu-Nb system was explored using atomistic modeling and anisotropic elastic theory, and it was shown that such interfaces are very strong traps for dislocation and thus effective barriers for slip transmission.

245 citations

Journal ArticleDOI
TL;DR: In this article, the effects of edge structures on the edge stability, and electronic and magnetic properties of MoS2 nanoribbons by first-principles calculations were studied. And the authors predicted that S-terminated zigzag nanors are the most stable even without hydrogen saturation because of their low and negative edge energies.
Abstract: Two-dimensional materials have various applications in next-generation nanodevices because of their easy fabrication and particular properties. In this work, we studied the effects of edge structures on the edge stability, and electronic and magnetic properties of MoS2 nanoribbons by first-principles calculations. We predicted that S-terminated zigzag nanoribbons are the most stable even without hydrogen saturation because of their low and negative edge energies, although hydrogen saturation of the edge states can stabilize other nanoribbons with different edge structures. MoS2 zigzag nanoribbons are metallic and ferromagnetic. Importantly, their conductivity may be semiconducting (n- or p-type) or half metallic by controlling the edge structures saturated with H atoms. The magnetic states of the MoS2 zigzag nanoribbons are enhanced by H-saturation and are much stronger than those of graphene zigzag nanoribbons. The armchair nanoribbons are semiconducting, with bandgaps increased by the hydrogen saturation of their edge states, and are nonmagnetic. These MoS2 nanoribbons with versatile functions may have applications in spintronics, nanodevices, and energy harvesting.

245 citations

Journal ArticleDOI
TL;DR: In this paper, the atomic and electronic properties of black phosphorus (BP) were studied via ab initio calculations, which revealed that the interlayer interaction in BP is Van der Waals Keesom force, which is critical to the formation of the layered structure.
Abstract: The atomic and electronic properties of black phosphorus (BP), which has been recently shown to have potential application as anode material for lithium ion batteries, are studied via ab initio calculations. The calculations reveal that the interlayer interaction in BP is Van der Waals Keesom force, which is critical to the formation of the layered structure. Interestingly, we also found that the small band gap of bulk BP (0.19 eV) when compared with that of single layer BP (0.75 eV) is partly because of the interlayer Van der Waals interaction in BP. The change in a materials band structure because of Van der Waals interaction is rarely reported in literature.

245 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