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 authors identify a previously unrecognized family of single-layer III-V materials and determine their energetic and dynamical stability, identify a surprising reconstruction, and calculate their electronic properties using a hybrid density functional.
Abstract: Single-layer materials open up tremendous opportunities for nanoelectronic devices. Using a first-principles design approach we identify a previously unrecognized family of single-layer III-V materials. We determine their energetic and dynamical stability, identify a surprising reconstruction, and calculate their electronic properties using a hybrid density functional and the ${G}_{0}{W}_{0}$ method. Finally, we find that metal substrates stabilize these as-yet hypothetical materials. Our results provide guidance for experimental synthesis efforts and future searches of single-layer materials suitable for device applications.
301 citations
TL;DR: In this paper, the results of ab initio LDA/GGA computations for the following systems are reported: AgAu, AgCd, AgMg, AgMo, AgNb∗, AgPd,AgRh, AgRu, AgTc, AgTi, AgY, AgZr, AlSc, AuCd.
Abstract: Predicting and characterizing the crystal structure of materials is a key problem in materials research and development. We report the results of ab initio LDA/GGA computations for the following systems: AgAu, AgCd, AgMg, AgMo∗, AgNa, AgNb∗, AgPd, AgRh∗, AgRu∗, AgTc∗, AgTi, AgY, AgZr, AlSc, AuCd, AuMo∗, AuNb, AuPd, AuPt∗, AuRh∗, AuRu∗, AuSc, AuTc∗, AuTi, AuY, AuZr, CdMo∗, CdNb∗, CdPd, CdPt, CdRh, CdRu∗, CdTc∗, CdTi, CdY, CdZr, CrMg∗, MoNb, MoPd, MoPt, MoRh, MoRu, MoTc∗, MoTi, MoY ∗, MoZr, NbPd, NbPt, NbRh, NbRu, NbTc, NbY ∗, NbZr∗, PdPt, PdRh∗, PdRu∗, PdTc, PdTi, PdY, PdZr, PtRh, PtRu, PtY, PtTc, PtTi, PtZr, RhRu, RhTc, RhTi, RhY, RhZr, RuTi, RuTc, RuY, RuZr, TcTi, TcY, TcZr, TiZr∗, Y Zr∗ (∗= systems in which the ab initio method predicts that no compounds are stable). A detailed comparison to experimental data confirms the high accuracy with which ab initio methods can predict ground states.
300 citations
TL;DR: In this article, the authors present density functional theory (DFT) calculations for MnO compounds using different gradient corrected functionals, such as Perdew-Burke-Ernzerhof (PBE), PBE+U, and the two hybrid density functional Hartree-Fock methods PBE0 and Heyd-Scuseria-Enzerhoff (HSE).
Abstract: We present density functional theory (DFT) calculations for MnO, ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$, $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Mn}}_{2}{\mathrm{O}}_{3}$, and $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Mn}{\mathrm{O}}_{2}$, using different gradient corrected functionals, such as Perdew-Burke-Ernzerhof (PBE), $\mathrm{PBE}+\mathrm{U}$, and the two hybrid density functional Hartree-Fock methods PBE0 and Heyd-Scuseria-Ernzerhof (HSE). We investigate the structural, electronic, magnetic, and thermodynamical properties of the mentioned compounds. Despite the lack of sufficient experimental information allowing for a comprehensive comparison of our results, we find overall that hybrid functionals provide a more consistent picture than standard PBE. Although $\mathrm{PBE}+\mathrm{U}$ is limited due to the uncertainty of choosing the parameter U, it nevertheless provides satisfactory results in terms of magnetic properties and energies of formation. This is in line with results of PBE0 and HSE calculations, but the $\mathrm{PBE}+\mathrm{U}$ approach tends to overestimate the equilibrium volumes, and also it favors a half-metallic state for the more reduced oxides ${\mathrm{Mn}}_{3}{\mathrm{O}}_{4}$, $\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{Mn}}_{2}{\mathrm{O}}_{3}$, and $\ensuremath{\beta}\text{\ensuremath{-}}\mathrm{Mn}{\mathrm{O}}_{2}$, rather than an insulating character as derived from the hybrid functional approaches. The comparison of measured valence-band spectra with the HSE density of states offers a further assessment of the capability of hybrid approaches in overcoming the deficiencies of DFT in treating these kinds of materials.
299 citations
TL;DR: The results suggest that single-layer and double-layer SnSe and GeSe are promising materials for ultrathin-film photovoltaic applications with theoretical upper bounds to the conversion efficiency that approach the efficiency records realized in organic and dye-sensitized solar cells.
Abstract: SnSe and GeSe are layered compound semiconductors that can be exfoliated to form two-dimensional materials. In this work, we use predictive calculations based on density functional and many-body perturbation theory to study the electronic and optical properties of single-layer, double-layer, and bulk SnSe and GeSe. The fundamental band gap is direct in single-layer and double-layer GeSe, but indirect in single-layer and double-layer SnSe. Moreover, the interplay of spin–orbit coupling and lack of inversion symmetry in the monolayer structures results in anisotropic spin splitting of the energy bands, with potential applications in directionally dependent spin transport. We also show that single-layer and double-layer SnSe and GeSe exhibit unusually strong optical absorbance in the visible range. Our results suggest that single-layer and double-layer SnSe and GeSe are promising materials for ultrathin-film photovoltaic applications with theoretical upper bounds to the conversion efficiency that approach th...
299 citations
TL;DR: In this article, the structural stability and electronic band structure of all three copper oxide compounds were investigated using ab initio methods within the framework of density functional theory and consider different exchange correlation functionals.
Abstract: The $p$-type semiconductor copper oxide has three distinct phases Cu${}_{2}$O, CuO, and Cu${}_{4}$O${}_{3}$ with different morphologies and oxidation states of the copper ions. We investigate the structural stability and electronic band structure of all three copper oxide compounds using ab initio methods within the framework of density functional theory and consider different exchange correlation functionals. While the local density approximation (LDA) fails to describe the semiconducting states of CuO and Cu${}_{4}$O${}_{3}$, the $\mathrm{LDA}+U$ and HSE06 hybrid functional describe both compounds as indirect semiconductors. Using the HSE06 hybrid functional we calculate the electronic band structure in the full Brillouin zone for all three copper oxide compounds.
299 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