The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Emily A. Carter - One of the best experts on this subject based on the ideXlab platform.
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Ultrasoft spin-dependent Pseudopotentials.
The Journal of chemical physics, 2005Co-Authors: Vincent Cocula, Chris J. Pickard, Emily A. CarterAbstract:The use of the spin-dependent Pseudopotentials has been shown to markedly enhance the transferability of the commonly used spin-neutral Pseudopotential method for the study of the structural and magnetic properties of transition-metal-containing materials. Unfortunately, because the method was based on the rather expensive norm-conserving Pseudopotential formalism, the method was limited to the study of fairly small systems. Here we present an extension of the spin-dependent Pseudopotential method for the far more computationally advantageous ultrasoft formalism and show that it is very easy to add such a feature to any preexisting computer code. We benchmark our new method by comparing to previously published results and then apply it to the study of several relevant test cases: bulk Ni, Fe, and Co, as well as a Pd atomic wire.
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Breakdown of the Pseudopotential approximation for magnetic systems: Predicting magnetic quenching at the V(001) surface with spin-dependent Pseudopotentials
Physical Review B, 2004Co-Authors: Vincent Cocula, Emily A. CarterAbstract:Both experimentally [R.L. Fink et al., Phys. Rev. B 41, 10 175 (1990)] and using all-electron density-functional theory (DFT) method, the V(001) surface exhibits little or no magnetization. Very recently, independent Pseudopotential DFT calculations demonstrated the breakdown of the Pseudopotential approximation, showing large magnetic moments at the surface of a V(001) slab. Here we demonstrate that use of spin-dependent Pseudopotentials systematically corrects the inaccuracies of conventional spin-neutral Pseudopotentials, producing results consistent with all-electron ones. We also show how the use of the spin-dependent Pseudopotentials allows one to achieve a high level of accuracy without the numerical difficulties and cost associated with accurate spin-neutral Pseudopotentials.
Vincent Cocula - One of the best experts on this subject based on the ideXlab platform.
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Ultrasoft spin-dependent Pseudopotentials.
The Journal of chemical physics, 2005Co-Authors: Vincent Cocula, Chris J. Pickard, Emily A. CarterAbstract:The use of the spin-dependent Pseudopotentials has been shown to markedly enhance the transferability of the commonly used spin-neutral Pseudopotential method for the study of the structural and magnetic properties of transition-metal-containing materials. Unfortunately, because the method was based on the rather expensive norm-conserving Pseudopotential formalism, the method was limited to the study of fairly small systems. Here we present an extension of the spin-dependent Pseudopotential method for the far more computationally advantageous ultrasoft formalism and show that it is very easy to add such a feature to any preexisting computer code. We benchmark our new method by comparing to previously published results and then apply it to the study of several relevant test cases: bulk Ni, Fe, and Co, as well as a Pd atomic wire.
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Breakdown of the Pseudopotential approximation for magnetic systems: Predicting magnetic quenching at the V(001) surface with spin-dependent Pseudopotentials
Physical Review B, 2004Co-Authors: Vincent Cocula, Emily A. CarterAbstract:Both experimentally [R.L. Fink et al., Phys. Rev. B 41, 10 175 (1990)] and using all-electron density-functional theory (DFT) method, the V(001) surface exhibits little or no magnetization. Very recently, independent Pseudopotential DFT calculations demonstrated the breakdown of the Pseudopotential approximation, showing large magnetic moments at the surface of a V(001) slab. Here we demonstrate that use of spin-dependent Pseudopotentials systematically corrects the inaccuracies of conventional spin-neutral Pseudopotentials, producing results consistent with all-electron ones. We also show how the use of the spin-dependent Pseudopotentials allows one to achieve a high level of accuracy without the numerical difficulties and cost associated with accurate spin-neutral Pseudopotentials.
Hermann Stoll - One of the best experts on this subject based on the ideXlab platform.
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energy consistent Pseudopotentials and correlation consistent basis sets for the 5d elements hf pt
Journal of Chemical Physics, 2009Co-Authors: Detlev Figgen, Kirk A Peterson, Michael Dolg, Hermann StollAbstract:New relativistic energy-consistent Pseudopotentials have been generated for the 5d transition metals Hf–Pt. The adjustment was done in numerical two-component multiconfiguration Hartree–Fock calculations, using atomic valence-energy spectra from four-component multiconfiguration Dirac–Hartree–Fock calculations as reference data. The resulting two-component Pseudopotentials replace the [Kr]4d104f14 cores of the 5d transition metals and can easily be split into a scalar-relativistic and a spin-orbit part. They reproduce the all-electron reference energy data with deviations of ∼0.01 eV for configurational averages and ∼0.05 eV for individual relativistic states. Full series of correlation consistent basis sets from double to quintuple-zeta have also been developed in this work for use with the new Pseudopotentials. In addition, all-electron triple-zeta quality correlation consistent basis sets are also reported in order to provide calibration for the Pseudopotential treatment. The accuracy of both the pseud...
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The accuracy of the Pseudopotential approximation. III. A comparison between Pseudopotential and all-electron methods for Au and AuH
The Journal of Chemical Physics, 2000Co-Authors: Peter Schwerdtfeger, J. Reuben Brown, Jon K. Laerdahl, Hermann StollAbstract:The quality of the Pseudopotential approximation has been tested thoroughly by calculating spectroscopic properties of the gold atom and ground state AuH for eight different effective core potentials using Hartree–Fock, second-order Mo/ller–Plesset and coupled cluster methods. The Pseudopotential valence basis set {φ}v for Au was chosen to be identical for all Pseudopotentials, a subset of the all-electron basis set {φ}v⊂{φ}AE, and the condition was applied that all sets are of near basis set limit quality. The Pseudopotential results are compared with data obtained from nonrelativistic, scalar relativistic Douglas–Kroll and fully relativistic four-component all-electron calculations. The variation between the results obtained for all valence electron small-core Pseudopotentials and all electron Douglas–Kroll calculations is found to be small (for the Stuttgart Pseudopotential Δre=0.001 A, ΔDe=0.03 eV, Δωe=9 cm−1, Δμe=0.04 D). Sizable differences to all electron results are only found for the 11 valence e...
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the accuracy of the Pseudopotential approximation ii a comparison of various core sizes for indium Pseudopotentials in calculations for spectroscopic constants of inh inf and incl
Journal of Chemical Physics, 1996Co-Authors: Thierry Leininger, Hermann Stoll, Michael Dolg, Andreas Nicklass, Peter SchwerdtfegerAbstract:Small‐ and medium‐core Pseudopotentials representing [Ar]3d10‐ and [Kr]‐like cores, respectively, have been adjusted for the In atom, supplementing the energy‐consistent three‐valence‐electron large‐core ([Kr]4d10 core) Pseudopotential of the Stuttgart group. The performance of these potentials is tested against those of other groups and against experiment, in calculations for the ground‐state potential curves of InH, InF, and InCl, both at the self‐consistent‐field and correlated levels. The role of the core size is discussed, and systematic errors of large‐ and medium‐core Pseudopotentials are analyzed.
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a combination of quasirelativistic Pseudopotential and ligand field calculations for lanthanoid compounds
Theoretical Chemistry Accounts, 1993Co-Authors: Michael Dolg, Hermann Stoll, H PreussAbstract:Improved energy-adjusted quasirelativistic Pseudopotentials for lanthanoid atoms with fixed valency are presented and tested in molecular calculations for CeO, CeF, EuO, GdO, YbO, and YbF. The Pseudopotential calculations treat the lanthanoid 4f shell as part of the core and yield accurate estimates for average bond lengths, vibrational frequencies and dissociation energies of all states belonging to a superconfiguration. Information for each individual state of the considered superconfiguration may be obtained from subsequent ligand field model calculations. The results of this combined pseudo-potential and ligand field approach (PPLFT) are compared to more accurate calculations with ab initio Pseudopotentials that include the lanthanoid 4f orbitals explicitly in the valence shell and to available experimental data.
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Pseudopotential approaches to ca sr and ba hydrides why are some alkaline earth mx2 compounds bent
Journal of Chemical Physics, 1991Co-Authors: Martin Kaupp, Hermann Stoll, Paul V R Schleyer, H PreussAbstract:Quasirelativistic and nonrelativistic 10‐valence‐electron Pseudopotentials for Ca, Sr, and Ba are presented. Results of calculations with 6s6p5d basis sets for MH, MH+, and MH2 are compared with all‐electron and 2‐valence‐electron Pseudopotential calculations with and without core‐polarization potentials. The 10‐valence‐electron Pseudopotential approach agrees well with all‐electron calculations. It circumvents problems for the 2‐valence‐electron Pseudopotentials arising from an incomplete separation of valence and subvalence shells in polar molecular systems due to strongly contracted occupied (n−1)‐d orbitals. All higher‐level calculations show SrH2 and BaH2 to be bent with angles of ∼140° and 120°, respectively, while CaH2 is linear with a flat potential‐energy surface for the bending motion. The use of a core‐polarization potential together with the 2‐valence‐electron Pseudopotential approach allows an investigation of the relative importance of core‐polarization vs direct d‐orbital bonding participation as reasons for the bent structures. The calculations strongly suggest that both contribute to the bending in SrH2 and BaH2. Even at the Hartree–Fock level of theory 10‐valence‐electron Pseudopotential calculations given reasonable angles when the potential‐energy surface is not exceedingly flat, and only moderately contracted basis sets including both compact d functions and diffuse p functions are used. The effect of core‐valence correlation and the importance of f functions also are discussed.
G Dente - One of the best experts on this subject based on the ideXlab platform.
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Empirical Pseudopotential Modeling of Superlattices
2005Co-Authors: A. P. Ongstad, Maryam Tilton, G DenteAbstract:Abstract : For several years, we have been accurately calculating the electronic structure of superlattices using a solution technique based on the Empirical Pseudopotential Method (EOM). In our method for forming the superlattice Pseudopotential, the critical assumption is that the heterointerface charges are redistributed, making each constituent layer in the superlattice as bulk-like as possible. Here, we demonstrate that our technique for forming the superlattice Pseudopotential is fundamentally different from the atomistic Pseudopotential approaches that use a superposition of atomic Pseudopotentials to represent the superlattice. We then present several applications of our method to InAsGaSb Type-II superlattices and, where possible, we compare our results to those calculated with an effective mass method, as well as to atomistic EPM methods. In all of these comparisons, our method provides excellent agreement with the measured data.
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Comparing Pseudopotential predictions for InAs/GaSb superlattices
Physical Review B, 2002Co-Authors: G Dente, Maryam TiltonAbstract:For several years, we have been accurately calculating the electronic structure of superlattices using a solution technique based on the empirical Pseudopotential method. In our method for forming the superlattice Pseudopotential, the critical assumption is that the heterointerface charges are redistributed, making each constituent layer in the superlattice as bulklike as possible. Here, we demonstrate that our technique for forming the superlattice Pseudopotential is fundamentally different from the atomistic Pseudopotential approaches that use a superposition of atomic Pseudopotentials to represent the superlattice. We then present several applications of our method to InAs-GaSb type-II superlattices and, where possible, we compare our results to those calculated with an effective mass method, as well as to atomistic Pseudopotential methods. In all of these comparisons, our method provides excellent agreement with the measured data.
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comparing Pseudopotential predictions for inas gasb superlattices
Physical Review B, 2002Co-Authors: G Dente, M L TiltonAbstract:For several years, we have been accurately calculating the electronic structure of superlattices using a solution technique based on the empirical Pseudopotential method. In our method for forming the superlattice Pseudopotential, the critical assumption is that the heterointerface charges are redistributed, making each constituent layer in the superlattice as bulklike as possible. Here, we demonstrate that our technique for forming the superlattice Pseudopotential is fundamentally different from the atomistic Pseudopotential approaches that use a superposition of atomic Pseudopotentials to represent the superlattice. We then present several applications of our method to InAs-GaSb type-II superlattices and, where possible, we compare our results to those calculated with an effective mass method, as well as to atomistic Pseudopotential methods. In all of these comparisons, our method provides excellent agreement with the measured data.
H Preuss - One of the best experts on this subject based on the ideXlab platform.
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a combination of quasirelativistic Pseudopotential and ligand field calculations for lanthanoid compounds
Theoretical Chemistry Accounts, 1993Co-Authors: Michael Dolg, Hermann Stoll, H PreussAbstract:Improved energy-adjusted quasirelativistic Pseudopotentials for lanthanoid atoms with fixed valency are presented and tested in molecular calculations for CeO, CeF, EuO, GdO, YbO, and YbF. The Pseudopotential calculations treat the lanthanoid 4f shell as part of the core and yield accurate estimates for average bond lengths, vibrational frequencies and dissociation energies of all states belonging to a superconfiguration. Information for each individual state of the considered superconfiguration may be obtained from subsequent ligand field model calculations. The results of this combined pseudo-potential and ligand field approach (PPLFT) are compared to more accurate calculations with ab initio Pseudopotentials that include the lanthanoid 4f orbitals explicitly in the valence shell and to available experimental data.
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Pseudopotential approaches to ca sr and ba hydrides why are some alkaline earth mx2 compounds bent
Journal of Chemical Physics, 1991Co-Authors: Martin Kaupp, Hermann Stoll, Paul V R Schleyer, H PreussAbstract:Quasirelativistic and nonrelativistic 10‐valence‐electron Pseudopotentials for Ca, Sr, and Ba are presented. Results of calculations with 6s6p5d basis sets for MH, MH+, and MH2 are compared with all‐electron and 2‐valence‐electron Pseudopotential calculations with and without core‐polarization potentials. The 10‐valence‐electron Pseudopotential approach agrees well with all‐electron calculations. It circumvents problems for the 2‐valence‐electron Pseudopotentials arising from an incomplete separation of valence and subvalence shells in polar molecular systems due to strongly contracted occupied (n−1)‐d orbitals. All higher‐level calculations show SrH2 and BaH2 to be bent with angles of ∼140° and 120°, respectively, while CaH2 is linear with a flat potential‐energy surface for the bending motion. The use of a core‐polarization potential together with the 2‐valence‐electron Pseudopotential approach allows an investigation of the relative importance of core‐polarization vs direct d‐orbital bonding participation as reasons for the bent structures. The calculations strongly suggest that both contribute to the bending in SrH2 and BaH2. Even at the Hartree–Fock level of theory 10‐valence‐electron Pseudopotential calculations given reasonable angles when the potential‐energy surface is not exceedingly flat, and only moderately contracted basis sets including both compact d functions and diffuse p functions are used. The effect of core‐valence correlation and the importance of f functions also are discussed.