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Sökning: WFRF:(Wills John M)

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1.
  • Kanai, M, et al. (författare)
  • 2023
  • swepub:Mat__t
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2.
  • Falster, Daniel, et al. (författare)
  • AusTraits, a curated plant trait database for the Australian flora
  • 2021
  • Ingår i: Scientific Data. - : Nature Portfolio. - 2052-4463. ; 8:1
  • Tidskriftsartikel (refereegranskat)abstract
    • We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge.
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3.
  • Lejaeghere, Kurt, et al. (författare)
  • Reproducibility in density functional theory calculations of solids.
  • 2016
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 351:6280, s. 1415-1422
  • Tidskriftsartikel (refereegranskat)abstract
    • The widespread popularity of density functional theory has given rise to an extensive range of dedicated codes for predicting molecular and crystalline properties. However, each code implements the formalism in a different way, raising questions about the reproducibility of such predictions. We report the results of a community-wide effort that compared 15 solid-state codes, using 40 different potentials or basis set types, to assess the quality of the Perdew-Burke-Ernzerhof equations of state for 71 elemental crystals. We conclude that predictions from recent codes and pseudopotentials agree very well, with pairwise differences that are comparable to those between different high-precision experiments. Older methods, however, have less precise agreement. Our benchmark provides a framework for users and developers to document the precision of new applications and methodological improvements.
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4.
  • van Es, Michael A, et al. (författare)
  • Angiogenin variants in Parkinson disease and amyotrophic lateral sclerosis
  • 2011
  • Ingår i: Annals of Neurology. - : Wiley-Blackwell. - 0364-5134 .- 1531-8249. ; 70:6, s. 964-973
  • Tidskriftsartikel (refereegranskat)abstract
    • OBJECTIVE: Several studies have suggested an increased frequency of variants in the gene encoding angiogenin (ANG) in patients with amyotrophic lateral sclerosis (ALS). Interestingly, a few ALS patients carrying ANG variants also showed signs of Parkinson disease (PD). Furthermore, relatives of ALS patients have an increased risk to develop PD, and the prevalence of concomitant motor neuron disease in PD is higher than expected based on chance occurrence. We therefore investigated whether ANG variants could predispose to both ALS and PD.METHODS: We reviewed all previous studies on ANG in ALS and performed sequence experiments on additional samples, which allowed us to analyze data from 6,471 ALS patients and 7,668 controls from 15 centers (13 from Europe and 2 from the USA). We sequenced DNA samples from 3,146 PD patients from 6 centers (5 from Europe and 1 from the USA). Statistical analysis was performed using the variable threshold test, and the Mantel-Haenszel procedure was used to estimate odds ratios.RESULTS: Analysis of sequence data from 17,258 individuals demonstrated a significantly higher frequency of ANG variants in both ALS and PD patients compared to control subjects (p = 9.3 × 10(-6) for ALS and p = 4.3 × 10(-5) for PD). The odds ratio for any ANG variant in patients versus controls was 9.2 for ALS and 6.7 for PD.INTERPRETATION: The data from this multicenter study demonstrate that there is a strong association between PD, ALS, and ANG variants. ANG is a genetic link between ALS and PD.
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5.
  • Björkman, Torbjörn, 1977-, et al. (författare)
  • Self-interaction correction scheme for a full-potential linear muffin-tin orbital method
  • Annan publikation (populärvet., debatt m.m.)abstract
    • The self-interaction correction has been implemented in a full-potential linear muffin-tin orbital (FP-LMTO) scheme. The method is tested on several known materials where self-interaction is important; transition metal oxides and rare-earth elements. We find in general good agreement with previous implementations based on the atomic-sphere approximation. The implementation can be used for an crystal structure, without geometrical constraints. In addition, it is possible to consider non-spherical components to the electron density, which in self-interaction corrected electronic structure methods poses a particularly challenging problem, which is analyzed in detail.
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6.
  • Björkman, Torbjörn, 1977-, et al. (författare)
  • Theoretical studies of the incommensurate magnetic structure of a heavy fermion system: CeRhIn5
  • 2010
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 81:9, s. 094433-
  • Tidskriftsartikel (refereegranskat)abstract
    • We have investigated the electronic structure and the incommensurate magnetic configuration of the pressure-induced superconductor CeRhIn5. Noncollinear first-principles calculations were performed in the local-density approximation plus U scheme. The observed magnetic configuration is described accurately in our calculations, especially considering the minute energy scale which is relevant (microelectron volt). The band structure and Fermi surfaces were investigated and nesting was found to be responsible for the complex noncollinear magnetic state of CeRhIn5.
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7.
  • Ekholm, Marcus (författare)
  • Theoretical Descriptions of Complex Magnetism in Transition Metals and Their Alloys
  • 2012
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • In this thesis, various methods for studying solids by simulations of quantummechanical equations, have been applied to transition metals and their alloys. Transition metals such as Fe, Ni, and Mn, are not only cornerstones in modern technology, but also key components in the very fabric of the Earth interior. Such systems show highly complex magnetic properties. As shown within this thesis, to understand and predict their properties from a microscopic level, is still a highly demanding task for the the quantum theory of solids. This is especially crucial at elevated temperature and pressure.It is found that the magnetic degrees of freedom are inseparable from the structural, elastic and chemical properties of such alloy systems. This requires theoretical descriptions capable of handling this interplay. Such schemes are discussed and demonstrated.Furthermore, the importance of the description of Coulomb correlation effects is demonstrated by DFT calculations and also by going beyond the one-electron description by the LDA+DMFT method.It is also shown how magnetic interactions in the half-metallic compound NiMnSb can be manipulated by alloying. The stability of these alloys is  also evaluated in calculations, and verified by experimental synthesis at ambient conditions.
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8.
  • Eriksson, Olle, et al. (författare)
  • Many-body projector orbitals for electronic structure theory of strongly correlated electrons
  • 2005
  • Ingår i: INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY. - : Wiley. - 0020-7608 .- 1097-461X. ; 105:2, s. 160-
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe a technique to evaluate projector functions to be used, e.g., in self-interaction corrected versions of the Kohn-Sham equation (or in the LSDA+U method). The projector functions reproduce by construction the expectation values of spin and orbital moments (or any other property one is interested in) for the atomic many-body state. We therefore refer to these projector functions as many-body projector orbitals (MBPO). We describe how, once these projector states have been calculated, one can use them in any electronic structure method for a solid or molecule, to calculate ground-state properties of materials with strongly correlated states.
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9.
  • Grechnev, Alexei, et al. (författare)
  • Theory of bulk and surface quasiparticle spectra for Fe, Co, and Ni
  • 2007
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 76:3, s. 035107-
  • Tidskriftsartikel (refereegranskat)abstract
    • The correlated quasiparticle band structure of iron, cobalt, and nickel is investigated within the dynamical mean-field theory formalism using the recently developed full-potential linear-muffin-tin-orbital-based local-density approximation plus dynamical mean-field theory (LDA+DMFT) code. Detailed analysis of the calculated electron self-energy, density of states, and the spectral density is presented for these metals. It has been found that all these elements show strong correlation effects for majority-spin electrons, such as strong damping of quasiparticles and formation of a satellite state below the bottom of d bands. In particular, our work clearly predicts the existence of a photoemission satellite for bcc iron. The LDA+DMFT data for fcc nickel and cobalt (111) surfaces and bcc iron (001) surface are also presented. The electron self-energy is found to depend strongly on the number of nearest neighbors, and it practically reaches the bulk value already in the second layer from the surface. The dependence of correlation effects on the dimensionality of the problem is also discussed.
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10.
  • Hugosson, Håkan Wilhelm, 1972-, et al. (författare)
  • Theory of phase stabilities and bonding mechanisms in stoichiometric and substoichiometric molybdenum carbide
  • 1999
  • Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 86:7, s. 3758-3767
  • Tidskriftsartikel (refereegranskat)abstract
    • ABSTRACTFirst principles, total energy methods have been applied to predict the relative stabilities of the four experimentally verified MoC phases: the cubic δ(NaCl) phase and the three hexagonal γ(WC), η and γ′(TiAs) phases. The effect of vacancies on the relative stability of these four phases was investigated using a model structure with ordered vacancies within the carbon sublattice. For stoichiometric MoC, the γ phase was found to be the most stable followed by γ′, δ, and η, but for substoichiometric MoC0.75,MoC0.75, the order of relative stability was changed and the substoichiometric δ phase was found to have the lowest energy followed by γ′ and γ. A study of the electronic structure revealed vacancy induced peaks in the density of state and the electron density attached to these peaks was analyzed and found to emanate from unscreened Mo–Mo bonds through the carbon vacancy site. Finally, the oxygen stabilization of the γ′ MoC phase was studied.
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11.
  • Mattsson, Ann E., et al. (författare)
  • The AM05 density functional applied to solids
  • 2008
  • Ingår i: Journal of Chemical Physics. - : American Institute of Physics (AIP). - 0021-9606 .- 1089-7690. ; 128:8, s. 084714-
  • Tidskriftsartikel (refereegranskat)abstract
    • We show that the AM05 functional [Armiento and Mattsson, Phys. Rev. B 72, 085108 (2005)] has the same excellent performance for solids as the hybrid density functionals tested in Paier et al. [J. Chem. Phys. 124, 154709 (2006); 125, 249901 (2006)]. This confirms the original finding that AM05 performs exceptionally well for solids and surfaces. Hartree-Fock hybrid calculations are typically an order of magnitude slower than local or semilocal density functionals such as AM05, which is of a regular semilocal generalized gradient approximation form. The performance of AM05 is on average found to be superior to selecting the best of local density approximation and PBE for each solid. By comparing data from several different electronic-structure codes, we have determined that the numerical errors in this study are equal to or smaller than the corresponding experimental uncertainties. (C) 2008 American Institute of Physics.
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12.
  • Wills, John M., et al. (författare)
  • A Database of Electronic Structures
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 179-181
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • In this short chapter, an data-base of electronic structures are described and a method in data-mining technology is presented, for how such a data-basemight be used to search for new functional materials.
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13.
  • Wills, John M., et al. (författare)
  • Chemical Bonding of Solids
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 111-131
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • In this chapter an analysis of chemical binding of materials is made, introducing concepts like the crystal orbital overlap population. Numerical examples of equilibrium volume of the transition metals, lanthanides and actinides are presented. Calculated equilibrium volumes of refractory materials are compared to experimental values. The cohesive energy is defined, and calculations are compared to experiment for the lanthanides. The structural stability of sp-bonded metals, transition metals, and actinides is discussed. In addition calculations of mixed valent materials, using the Kimbal–Falicov model are described. The chapter ends with a description of calculations of elastic constants of materials. For all calculations a comment on convergence of different computational parameters is made.
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14.
  • Wills, John M., et al. (författare)
  • Consequences of Infinite Crystals and Symmetries
  • 2010
  • Ingår i: Springer Series in Solid-State Sciences. - Berlin, Heidelberg : Springer Nature. ; , s. 21-24
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • In this short chapter the consequences of periodicity and general symmetry of a crystal is presented. The seven crystal lattices are introduced and as an example the point group operations of a cubic material are illustrated.
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15.
  • Wills, John M., et al. (författare)
  • Density Functional Theory and the Kohn–Sham Equation
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 7-19
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • The basic formulas of density functional theory (DFT) are derived, together with a discussion about the form and accuracy of different approximations to the energy functional used in DFT. Central concepts in DFT, like exchange and correlation hole, exchange and correlation energy, and the Kohn–Sham equation are presented. A short description about the historical development of density functional theory as also given.
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16.
  • Wills, John M., et al. (författare)
  • Dynamical Mean Field Theory
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 75-87
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • The basic reasons for why the common approximation to the exchange and correlation energy of density functional theory is inaccurate for certain materials are outlined. A possible fix to this problem, in terms of dynamical mean field theory (DMFT) is described, and details of how it is implemented in the FP-LMTO method are presented. The different choices of correlated orbitals which are to be considered in DMFT are also given. Examples of DMFT calculations are presented using different approximations to the ‘impurity part’ of the DMFT calculations.
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17.
  • Wills, John M., et al. (författare)
  • Excitated State Properties
  • 2010
  • Ingår i: Springer Series in Solid-State Sciences. - Berlin, Heidelberg : Springer Nature. ; , s. 145-178
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • The phenomenological theory of optical properties of materials is presented.The general theory of calculations of optical properties from first principlestheory is given, with special emphasis on the implementation in the FP-LMTOmethod. Numerical examples of semi-conductors as well as metals are presented. Interbandand intraband transitions are discussed, as are maneto-optical effects. Thechapter ends with a description of the theory of x-ray magnetic circular dichroism,and how its calculation is made possible in the FP-LMTO method.
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18.
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19.
  • Wills, John M., et al. (författare)
  • Future Developments and Outlook
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 183-185
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • In this final chapter a short summary and outlook is presented. In addition,future, anticipated developments of the FP-LMTO method are listed.
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20.
  • Wills, John M., et al. (författare)
  • Implementation
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 89-93
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • Details of the implementation of the FP-LMTO method are presented in this chapter. This includes programming language, routines for numerical operations like diagonalization and fast Fourier transforms, and parallelization aspects.
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21.
  • Wills, John M., et al. (författare)
  • Introduction to Electronic Structure Theory
  • 2010
  • Ingår i: Springer Series in Solid-State Sciences. - Berlin, Heidelberg : Springer Nature. ; , s. 25-34
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • An introduction to electronic structure theory of solids is presented, including the general form of the one-electron wave function. The evaluation of the electron density, density of states as well as the calculation of energy bands is described. Different types of integration of reciprocal space are presented, and numerical examples given for their accuracy. The calculation of a self-consistent field is also described, as is the Rayleigh-Ritz variational method.
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22.
  • Wills, John M., et al. (författare)
  • Introductory Information
  • 2010
  • Ingår i: Springer Series in Solid-State Sciences. - Berlin, Heidelberg : Springer Nature. ; , s. 3-6
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • In this introductory chapter a short historical note on the history of linear muffin-tin orbital methods is given, together with general background information and units used throughout the book. The main objectives with the book are presented as well as information about web-based information, which easier enables using the full-potential linear muffin-tin orbitals method.
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23.
  • Wills, John M., et al. (författare)
  • Linear Muffin-Tin Orbital Method in the Atomic Sphere Approximation
  • 2010
  • Ingår i: Springer Series in Solid-State Sciences. - Berlin, Heidelberg : Springer Nature. ; , s. 35-46
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • In this chapter the linear muffin-tin orbitals (LMTO) are defined, which includes linearization of the radial part of the wave function, the ‘head’ and ‘tails’ of the basis functions, and the so called structure constant. The atomic sphere approximation (ASA) is introduced and a comparison between the Korringa–Kohn– Rostoker (KKR) method and the linear muffin-tin orbital method is made. The advantages and disadvantages of the LMTO-ASA method are discussed.
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24.
  • Wills, John M., et al. (författare)
  • Magnetism
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 133-143
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • Chapter 12 describes the theory of magnetism, with focus on spin and orbital moments, and the magnetic anisotropy. Numerical examples are presented, both for bulk and surfaces, and the particular symmetry aspects of relativistic oneelectron theory and magnetism are described. The different contributions to the magnetic anisotropy are analyzed, as are the often cumbersome aspects of a slow convergence of the calculation of the magnetic anisotropy with respect to the number of k-points.
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25.
  • Wills, John M., et al. (författare)
  • Obtaining RSPt from the Web
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 95-97
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • In this short chapter details of how to obtain the FP-LMTO code from the web site http://www.rspt.net are given. In addition, a short instruction on how to install the FP-LMTO code is presented.
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26.
  • Wills, John M., et al. (författare)
  • The Full-Potential Electronic Structure Problem and RSPt
  • 2010
  • Ingår i: Full-Potential Electronic Structure Method. - Berlin, Heidelberg : Springer Nature. ; , s. 47-73
  • Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
    • The full-potential methodology is presented in this chapter, with details of how the non-spherical electron density and potential are expanded in the muffintin regions, as well as the interstitial region. Details in the implementation of the full-potential linear muffin-tin orbitals (FP-LMTO) method are presented, with a general definition of the mathematical functions used and the symmetry aspects of these functions. The difference between a minimal, double and triple basis set is described, and numerical tests of the convergence of these basis functions are presented.
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