| 1. |
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| 2. |
- Ahuja, R., et al.
(författare)
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Electronic structure of Ti3SiC2
- 2000
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 76:16, s. 2226-2228
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Tidskriftsartikel (refereegranskat)
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| 3. |
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| 4. |
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| 5. |
- Andersson, Malte, 1941, et al.
(författare)
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”Minskande befolkning är inte problemet”
- 2020
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Ingår i: Dagens Nyheter. ; :1 augusti, DN-debatt
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Nätverket Population Matters Sweden: En uppmärksammad studie i The Lancet pekar mot en lägre befolkningsökning i världen än tidigare prognoser. Men en miljard människor till är fortfarande långt över vad jorden klarar. Befolkningstrenden måste snarare vända neråt, och det kräver åtgärder för att stärka kvinnors rättigheter världen över.
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| 6. |
- Andersson, Per H., et al.
(författare)
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Theoretical study of structural and electronic properties of VHx
- 1998
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 58:9, s. 5230-5235
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Tidskriftsartikel (refereegranskat)abstract
- We have calculated the change in the electronic structure and the distortion of the lattice in vanadium upon hydrogenation from first principles using the full-potential linear muffin-tin-orbital method and the linear augmented plane-wave method in the local-density approximation. The calculated hydrogen induced volume expansions agree with experiment and the change in the c/a ratio is also in good agreement with observations where such are available for single phase VHx. Among several changes in the electronic structure, we note a hybridization of the d band of vanadium with the hydrogen 1s band. We also observe an antiferromagnetically ordered moment at V/Vexp=1.08. The possibility of producing magnetic V by means of hydrogenation in combination with epitaxial growth is suggested.
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| 7. |
- Belonoshko, Anatoly B., et al.
(författare)
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Quasi ab initio molecular dynamic study of Cu melting
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:6, s. 3838-3844
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the melting of Cu theoretically by means of a molecular dynamic method employing the Sutton-Chen model for the interatomic interaction. This interaction has been fitted to reproduce results from first-principles self-consistent total-energy calculations within the local-density approximation using the full-potential linear-muffin-tin-orbital method for the bcc, fee, hcp, and liquid configurations. No experimental data were used to tune the potential. A large number of properties including equation of state, melting temperature, high-pressure melting curve, change of volume and entropy at melting, liquid structure, diffusion coefficient in liquid, and vacancy formation energy are all in good agreement with experimental data. Inclusion of the full potential energy of a liquid configuration in the fitting procedure is critical for obtaining good agreement with experiment. Different ways to calculate the melting transition are shown to produce very different results. The use of a large number of particles in combination with the solid-liquid interface as an initial configuration in the simulation is essential in order to obtain the correct melting temperatures.
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| 8. |
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| 9. |
- Bomström Aho, Erika
(författare)
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Villkor för lärande : Utbildning på språkintroduktionsprogrammet ur lärar- och elevperspektiv
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Using the third space theory, the overall aim of this thesis is to study and problematize conditions for learning which are provided for newly arrived students in the Language Introduction Program in upper secondary school. By highlighting factors that affect these students' education in four sub-studies, the study contributes in-depth knowledge about the Language Introduction Program. The program is one of five introductory programs in Swedish upper secondary school that admits newly arrived students from the ages of 16 to 19. The thesis adopts an ethnographically inspired approach and consists of four qualitative sub-studies that highlight factors and issues that affect the education of students in the program. The data consist of observations of lessons in five different subjects, interviews with teachers and students, and assessment material that looks at the prior knowledge and experiences of students. The theoretical framework of the thesis is Bhabha’s third space theory, which is employed for the analysis of the results and conclusions.The findings indicate that knowledge in Swedish and knowledge learned in Swedish schools is highly valued by the teachers. What teachers and students say demonstrates that knowledge of Swedish is perceived as key to employment and a place within society. The results also show that some school knowledge gained earlier by students, in addition to knowledge acquired in Swedish schools, is more highly valued and made visible in a different way than the knowledge gained in other ways. The findings also indicate that what teachers say about knowledge in relation to Language Introduction students positions the students as students not knowing Swedish, or as some of the participating teachers put it, students who do not "have the language", indicating specifically Swedish. The students themselves talk about how they lack Swedish and how they must learn Swedish, which corresponds then with what the teachers say. Furthermore, the results show that some teachers use the term "students without background" to refer to students with little or no experience of formal schooling. This makes knowledge gained through formal schooling visible, and knowledge gained in other ways by students "without background" invisible. A conclusion that can be drawn from this thesis is that the students at Language Introduction are stereotyped as students with different knowledge than expected, that the education on the program is not based on the students' conditions and that their opportunities for learning are therefore not equivalent to those of students in other programs in Swedish schools.
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| 10. |
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| 11. |
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| 12. |
- Colarieti-Tosti, Massimiliano, et al.
(författare)
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First-principles theory of intermediate-valence f-electron systems
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:9, s. 096403-
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Tidskriftsartikel (refereegranskat)abstract
- We propose a first-principles based method for calculating the electronic structure and total energy of solids in an intermediate-valence configuration. The method takes into account correlation effects (d-f Coulomb interaction) and many-body renormalization of the effective hybridization parameter of the f system. As an example, the formation of a pressure-induced intermediate-valence state in Yb is considered and its electronic structure and equation of state are calculated and compared to experimental data. The agreement is found to be excellent for both properties, and we argue that the developed method, which applies to any element or compound, provides for the first time a quantitative theoretical treatment of intermediate-valence materials.
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| 13. |
- Dallera, C., et al.
(författare)
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Understanding mixed valent materials : Effects of dynamical core-hole screening in high-pressure x-ray spectroscopy
- 2006
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 74:8, s. 081101-
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Tidskriftsartikel (refereegranskat)abstract
- Changes in the electronic structure of Yb, a material whose valence is modified under pressure, are observed with remarkable detail in x-ray absorption and emission data measured between ambient conditions and 20 GPa. These changes are reproduced by a theory that essentially does not rely on experimental parameters, and includes dynamical core-hole screening. From the combined experimental and theoretical data we can firmly establish on a quantitative level how the valency of an intermediate valence material is modified by pressure. In metallic Yb it increases from 2 to 2.55 +/- 0.05 between 0 and 20 GPa.
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| 14. |
- Delczeg-Czirjak, Erna Krisztina, 1978-, et al.
(författare)
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Ab initio study of structural and magnetic properties of Si-doped Fe2P
- 2010
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 82:8, s. 085103-
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Tidskriftsartikel (refereegranskat)abstract
- Ab initio electronic-structure methods are used to study the properties of Fe2P1-xSix in ferromagnetic and paramagnetic states. The site preference and lattice relaxation are calculated with the projector augmented wave method as implemented in the Vienna ab initio simulation package. The paramagnetic state is modeled by the disordered local magnetic moment scheme, and the chemical and magnetic disorder is treated using the coherent potential approximation in combination with the exact muffin-tin orbital formalism. The calculated lattice parameters, atomic positions, and magnetic properties are in good agreement with the experimental and other theoretical results. In contrast to the observation, for the ferromagnetic state the body centered ortho-rhombic structure (bco, space group I (mm2) under bar) is predicted to have lower energy than the hexagonal structure (hex, space group P (6) over bar 2m). The zero-point spin fluctuation energy difference is found to be large enough to stabilize the hex phase. For the paramagnetic state, the hex structure is calculated to be the stable phase and the computed total energy versus composition indicates a hex to bco crystallographic phase transition with increasing Si content. The phonon vibrational free energy, estimated from the theoretical equation of state, turns out to stabilize the hexagonal phase, whereas the electronic and magnetic entropies favor the low symmetry orthorhombic structure.
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| 15. |
- Delczeg-Czirjak, Erna K., et al.
(författare)
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Magnetic exchange interactions in B-, Si-, and As-doped Fe2P from first-principles theory
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 85:22, s. 224435-
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Tidskriftsartikel (refereegranskat)abstract
- Di-iron phosphide (Fe2P) is a parent system for a set of magnetocaloric materials. Although the magnetic ordering temperature (T-C = 215 K) of the stoichiometric composition is too low for room-temperature magnetic refrigeration, the partial replacement of P with B, Si, or As elements results in a steep increase in the magnetic ordering temperature. Doping leads to different equilibrium volumes and hexagonal axial ratios (c/a) within the same crystallographic phase over a wide concentration range. Here, using first principles theory, we decompose the change in the total magnetic exchange interaction upon doping into chemical and structural contributions, the latter including the c/a-ratio and volume effects. We demonstrate that for the investigated alloys the structural effect can be ascribed mainly to the decrease in the c/a ratio that strengthens the magnetic exchange interactions between the two Fe sublattices.
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| 16. |
- Delczeg-Czirjak, Erna Krisztina, et al.
(författare)
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Microscopic theory of magnetism in the magnetocaloric material Fe2P1-xTx (T = B and Si)
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:4, s. 045126-
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Tidskriftsartikel (refereegranskat)abstract
- Landau phenomenological theory in combination with first-principles calculations was used to reveal the origin of the metamagnetic nature and the unusually strong dependence of the ordering temperature with doping of the Fe2P compound. We show that the magnetism of the two sublattices occupied by Fe atoms has an entwined codependency, which is strongly influenced by alloying. We furthermore demonstrate that a constrained disordered local moment approach combined with Monte Carlo simulations can only reproduce the experimental ordering temperatures in these technologically important prototype alloys for magnetocaloric refrigeration.
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| 17. |
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| 18. |
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| 19. |
- Eriksson, Helene
(författare)
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Systematisk analys och lösning av pianistiskt tekniska problem : instuderingsmodell tillämpad på F. Chopins etyder op. 25
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The problem-area studied in the present thesis concerns pianistic technique, with special reference to the possibilities of enhancing the efficiency of pianistic practice and increasing the awareness of chosen strategies of practice. The main aim of the thesis was to develop, on the basis of literature and praxis, a model for the systematic analysis and solution of problems of pianistic technique, as a tool to realize musical intentions. In accordance with this aim, it seemed fruitful to take advantage of knowledge from a number of relevant disciplines (regarding for example, prerequisites for pianistic technique and the practical solution of musical and pianistic problems). Hereby the work has obtained an inter-disciplinary character. General Systems Theory and Systems Analysis were applied as theoretically and methodologically unifying bases, respectively. It may be pointed out that in the field of systems analysis a number of useful descriptive techniques have been developed and become well-established. These techniques and a specially designed model have been applied, partly to the musical structures which are dealt with both from a level-related and a block/line-related systems perspective, partly to the solution of problems of pianistic technique. In the latter case inter- as well as intra-musical factors are considered. To test and evaluate the special model it has been applied to Chopin’s 12 Etudes, Op. 25, and an artistic illustration of the results of this application has been given, partly through the playing of a piano concerto on stage and partly in the form of a DVD-recording. The suggested approach and the special model have proved suitable for organizing pianistic practice and for realizing musical intentions. It has proved possible: to develop a model for the systematic analysis and solution of problems of pianistic technique, as a tool to realize musical intentions; to apply this model to Chopin’s 12 Etudes, Op. 25; to give an artistic illustration of the results of this application, partly through the playing of a piano concerto on stage and partly in the form of a DVD-recording.
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| 20. |
- Eriksson, Mimmi, 1973-, et al.
(författare)
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Alcohol prevention in the Swedish workplace – who cares?
- 2004
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Ingår i: Contemporary Drug Problems. - 0091-4509 .- 2163-1808. ; 31:2, s. 263-285
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Tidskriftsartikel (refereegranskat)abstract
- In this article we discuss what interest, and whose interest, there is in working with alcohol and drug prevention in workplaces. As the Swedish alcohol policy has weakened, alternative ways for primary prevention are sought. Public reports have pointed out the workplace as one arena for prevention that could compensate for the government's diminishing alcohol control. Will this work? What conditions are necessary in order to work successfully with these issues in a corporate environment? Several studies have suggested that there is little interest in working with prevention in workplaces, and this study supports this finding. This study involved interviews at 16 companies in Sweden with personnel managers, employees (in focus groups), union representatives, and in some cases the company's health care department. In a preliminary stage the findings verified our hypothesis that the overall interest in primary prevention in reality is not that strong. The participants in the study believed that the responsibility lies in intervention when the alcohol or drug problem has arisen, and there is really not much the company can do to prevent people from using alcohol or drugs.
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| 21. |
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| 22. |
- Eriksson, Mimmi, et al.
(författare)
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Alkohol- och drogtester i svenskt arbetsliv
- 2001
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Ingår i: Arbetsmarknad & Arbetsliv. - 1400-9692 .- 2002-343X. ; 7:4, s. 225-238
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Tidskriftsartikel (refereegranskat)abstract
- Alkohol- och drogtester i arbetslivet är fortfarande en kontroversiell och komplex fråga, femton år efter att tester först började användas i Sverige. Problematiken och oklarheterna rör såväl juridiska, sociala som etiska aspekter. Dessutom saknas utvärderingar och forskning i Sverige om huruvida alkohol- och drogtester överhuvudtaget bidrar till att uppnå de målsättningar som kopplas till dem. Tre fall har varit uppe i Arbetsdomstolen (AD), men har inte i någon högre grad klargjort de otydligheter som finns. På arbetsgivarsidan har utfallen av domsluten dock tolkats som ett klartecken till att både införa och fortsätta med tester. Denna artikel syftar till att redogöra för dagsläget och problematiken med alkohol- och drogtester. Undersökningsresultat från telefonintervjuer med personalchefer på svenska företag presenteras.
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| 23. |
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| 24. |
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| 25. |
- Eriksson Tinghög, Mimmi, 1973-
(författare)
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Mission Impossible? Universal Alcohol Prevention at Workplaces in Sweden
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Since the mid 1990s, alcohol policy in Sweden has undergone major changes and the restrictive policy instruments have been weakened. Alternative and compensatory preventive measures have been sought and the workplace is repeatedly referred to as an important and appropriate arena for prevention. Universal methods, such as disseminating information and education programs, are seen as crucial in order for individuals to be able to make informed choices about their alcohol consumption.The overall purpose of this thesis is to analyze the prerequisites for and the possibilities and barriers associated with alcohol education programs at workplaces. The first paper investigates the general interest in alcohol prevention at workplaces where no interventions had been undertaken. The second paper is an effect study which investigates the effects of a short alcohol education program provided to those employed at a company in Stockholm. In the third paper, the effects of a day-long alcohol education program provided to all persons employed by a municipality are studied. The fourth paper is an interview study, in which the aim is to analyze how the participants in alcohol education programs view their participation and the content and legitimacy of the intervention.The findings suggest that interest in prevention at workplaces is low among employers. In addition, there are difficulties linked to implementation and evaluation, and in achieving and registering any substantial effects. The effect studies noted a significant increase in alcohol-related knowledge and that binge drinking decreased among those who drank the most. The employees found the education programs interesting and valuable but mostly for others, i.e. those who drink too much. Taken together, the studies suggest that it is not reasonable to believe that workplace-based prevention will become a common and effective measure or that it will compensate for the weakened alcohol policy in Sweden.
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| 26. |
- Fransson, Jonas, et al.
(författare)
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On the non-orthogonality problem in the description of quantum devices
- 1999
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 272:1-4, s. 28-30
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Tidskriftsartikel (refereegranskat)abstract
- An approach which allows to include the corrections from non-orthogonality of electron states in contacts and quantum dots is developed. Comparison of the energy levels and charge distributions of electrons in 1D quantum dot (QD) in equilibrium, obtained within orthogonal (OR) and non-orthogonal representations (NOR), with the exact ones shows that the NOR provides a considerable improvement, for levels below the top of barrier. The approach is extended to non-equilibrium states. A derivation of the tunneling current through a single potential barrier is performed using equations of motion for correlation functions. A formula for transient current derived by means of the diagram technique for Hubbard operators is given for the problem of QD with strongly correlated electrons interacting with electrons in contacts. The non-orthogonality renormalizes the tunneling matrix elements and spectral weights of Green functions.
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| 27. |
- G.E. Grechnev,, et al.
(författare)
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Electronic structure and magnetic properties of Lithium manganese spinels
- 2003
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Ingår i: J.Magn. Magn. Matt.. ; 258, s. 287-289
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Tidskriftsartikel (refereegranskat)abstract
- Electronic and magnetic structures of the spinel-type lithium–manganese oxides LixMn2O4, x=0,0.5,1, are studied ab initio by employing a full-potential LMTO method. The effect of the orthorhombic distortion on electronic structure and magnetism of LiMn2O4 was investigated, and our calculations do not show a substantial charge ordering at the structural transition from the cubic spinel to the orthorhombic structure.
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| 28. |
- Gevert, Börje Sten, 1956, et al.
(författare)
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Preparation of discrete colloidal ZSM-5 crystals with high Al-content
- 2011
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Ingår i: Journal of Porous Materials. - : Springer Science and Business Media LLC. - 1573-4854 .- 1380-2224. ; 18:6, s. 723-728
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Tidskriftsartikel (refereegranskat)abstract
- A new method for synthesis of discrete colloidal ZSM-5 particles with SiO(2)/Al(2)O(3) M ratios as low as 30 and sizes .4-1 micrometer has been developed. The relation between the synthesis parameters and synthesis yield, crystal structure, crystallinity, particle size and morphology was investigated. The synthesis yield increases and the deviation of the SiO(2)/Al(2)O(3) ratio in the product from that in synthesis mixture decreases with increasing autoclave temperature suggesting that the introduction of aluminium into the zeolite structure is favoured by high autoclave temperature during the synthesis and that temperature determines the lower limit of the SiO(2)/Al(2)O(3) ratio. The SiO(2)/Al(2)O(3) ratio in the synthesis mixture decreases with autoclave temperature suggesting that the introduction of aluminium into the zeolite structure is favoured by high autoclave temperature during the synthesis and that the temperature determines the lower limit of SiO(2)/Al(2)O(3) ratio. Synthesis mixture, aimed to yield a high SiO(2)/Al(2)O(3) ratio, gives smaller zeolite crystals, higher specific surface areas, higher geometric areas (external surface area of the crystals) and a more oval crystal shape compared with lower ratios, synthesised at the same temperature. Higher autoclave temperature during the synthesis gives larger zeolite crystals and a more hexagonal crystal shape compared with zeolites synthesised at lower temperatures, for the same SiO(2)/Al(2)O(3) ratios.
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| 29. |
- Grechnev, G. E., et al.
(författare)
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Electronic structure, magnetic, and cohesive properties of LixMn2O4 : Theory
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:17
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Tidskriftsartikel (refereegranskat)abstract
- The volume dependent electronic structure of the spinel-type lithium manganese oxides LixMn2O4, x=0,0.5,1, is studied ab initio by employing a full-potential electronic structure method. The electronic structure, total energies, open-circuit voltage, and magnetic moments were obtained for various spin configurations of LixMn2O4 in the cubic spinel structure and the low-temperature orthorhombic structure. The effect of magnetic ordering on the band structure and structural stability has been investigated and an antiferromagnetic ordering proved to be the ground state of the LixMn2O4 spinels. Our calculations show that the manganese majority t(2g) d band is filled for all LixMn2O4 compounds studied, and the filling of the minority t(2g) band is expected in the lithiation process. The lithium intercalation potential, bulk modulus, magnetic moments, and optical properties are calculated within the itinerant band approach and are found to be in good agreement with available experimental data, indicating, that the density-functional theory provides reliable electronic structure of the LixMn2O4 system. The effect of the orthorhombic distortion on electronic structure and magnetism of LiMn2O4 was investigated, and our calculations do not show a substantial charge ordering at the structural transition from the cubic spinel to the orthorhombic structure, as proposed earlier. Instead, the low-temperature orthorhombic structure is found to possess the lowest energy via a Jahn-Teller distortion driven by the d band.
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| 30. |
- Götmark, Frank, 1955, et al.
(författare)
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FN bör ha som mål att bromsa folkökningen
- 2018
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Ingår i: Svenska Dagbladet (SvD-Debatt, 22 juli).
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- I diskussionen om miljö och vår framtid bör också överbefolkning lyftas fram. Frågan undviks ofta i samhällsdebatten – trots att den är central. Vi uppmanar den svenska regeringen att ta upp frågan i FN, skriver flera debattörer.
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| 31. |
- Hugosson, Håkan Wilhelm, et al.
(författare)
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Phase stabilities and homogeneity ranges in 4d-transition-metal carbides : A theoretical study
- 2001
-
Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 6313:13
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles full-potential linear muffin-tin orbital calculations have been used to study the 4d-transition-metal cal bides ZrC, NbC, and MoC. The experimental phase diagrams at T = 0 of the refractory compounds ZrC, NbC, and MoC have been reproduced with great accuracy from first principles theory. The energy of for marion for these compounds has been calculated for several phases and stoichiometries in order to understand the differences in phase stabilities and the changes in homogeneity ranges found between these systems is explained. The results can be regarded as theoretical zero-temperature phase stability diagrams for the three compounds containing not only the experimentally verified but also hypothetical phases and many of the experimental properties and trends are reproduced and explained. A study of the changes and differences in electronic structure and bonding of the studied compounds, phases and stoichiometries is also presented. As a part of this study the hexagonal Me2C (Me being Zr, Nb, or Mo) phases were studied and the theoretical structures, with relaxed interlayer distances and lattice parameters, were obtained. The phase stabilities and electronic structure of the experimentally reported orthorhombic Nb2C and Mo2C phases were also studied.
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| 32. |
- Hugosson, Håkan Wilhelm, 1972-, et al.
(författare)
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Phase stabilities and homogeneity ranges in 4d-transition-metal carbides: A theoretical study
- 2001
-
Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 63:13
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles full-potential linear muffin-tin orbital calculations have been used to study the 4d-transition-metal carbides ZrC, NbC, and MoC. The experimental phase diagrams at T=0 of the refractory compounds ZrC, NbC, and MoC have been reproduced with great accuracy from first principles theory. The energy of formation for these compounds has been calculated for several phases and stoichiometries in order to understand the differences in phase stabilities and the changes in homogeneity ranges found between these systems is explained. The results can be regarded as theoretical zero-temperature phase stability diagrams for the three compounds containing not only the experimentally verified but also hypothetical phases and many of the experimental properties and trends are reproduced and explained. A study of the changes and differences in electronic structure and bonding of the studied compounds, phases and stoichiometries is also presented. As a part of this study the hexagonal Me2C (Me being Zr, Nb, or Mo) phases were studied and the theoretical structures, with relaxed interlayer distances and lattice parameters, were obtained. The phase stabilities and electronic structure of the experimentally reported orthorhombic Nb2C and Mo2C phases were also studied.
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| 33. |
- Hugosson, Håkan Wilhelm, et al.
(författare)
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Phase stabilities and structural relaxations in substoichiometric TiC1-x
- 2001
-
Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 6316:16, s. 165116-
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Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations have been used to study the effect of vacancies and relaxation around the vacancy sites in substoichiometric TiC1-x. The effect of relaxation on phase stabilities, equilibrium volumes. and electronic structure of the substoichiometric phases was studied using a combined approach of pseudopotential plane wave and full-potential linear muffin-tin orbital methods. A relaxation away from the vacancies was found for the titanium atoms, the magnitude of which increased with vacancy concentration and the inclusion of nearest-neighbor carbon atom relaxation. The inclusion of local relaxations was found to correctly predict the off-stoichiometric equilibrium composition of titanium carbide. The anomalous volume behavior of TiC at small vacancy concentration is explained as an effect of the local relaxation of the atoms surrounding the vacancy sites, but we do not find that the lattice parameter of any of the studied stoichiometries is larger than that of ideal stoichiometric TiC.
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| 34. |
- Hugosson, Håkan Wilhelm, 1972-, et al.
(författare)
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Phase stabilities and structural relaxations in substoichiometric TiC1−x
- 2001
-
Ingår i: Physical Review B Condensed Matter. - : American Physical Society. - 0163-1829 .- 1095-3795. ; 63:16
-
Tidskriftsartikel (refereegranskat)abstract
- First-principles calculations have been used to study the effect of vacancies and relaxation around the vacancy sites in substoichiometric TiC1−x. The effect of relaxation on phase stabilities, equilibrium volumes, and electronic structure of the substoichiometric phases was studied using a combined approach of pseudopotential plane wave and full-potential linear muffin-tin orbital methods. A relaxation away from the vacancies was found for the titanium atoms, the magnitude of which increased with vacancy concentration and the inclusion of nearest-neighbor carbon atom relaxation. The inclusion of local relaxations was found to correctly predict the off-stoichiometric equilibrium composition of titanium carbide. The anomalous volume behavior of TiC at small vacancy concentration is explained as an effect of the local relaxation of the atoms surrounding the vacancy sites, but we do not find that the lattice parameter of any of the studied stoichiometries is larger than that of ideal stoichiometric TiC.
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| 35. |
- Hugosson, Håkan Wilhelm, et al.
(författare)
-
Phase stability diagrams of transition metal carbides, a theoretical study
- 2001
-
Ingår i: CHEMICAL PHYSICS LETTERS. - 0009-2614 .- 1873-4448. ; 333:6, s. 444-450
-
Tidskriftsartikel (refereegranskat)abstract
- The experimental phase diagrams at T=0 of the refractory compounds ZrC, NbC and MoC have been reproduced with great accuracy from first principles theory. The energy of formation for these compounds has been calculated for several phases and stoichiometries in order to understand, for example, the differences and changes in homogeneity ranges found in these systems. This determination of relative phase stabilities for a wide range of concentrations is necessary for first principles determination of phase diagrams for these compounds with complex bonding and structural properties as well as technological importance.
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| 36. |
- Hugosson, Håkan Wilhelm, et al.
(författare)
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Restricting dislocation movement in transition metal carbides by phase stability tuning
- 2001
-
Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 293:5539, s. 2434-2437
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Tidskriftsartikel (refereegranskat)abstract
- A mechanism to enhance hardness in multilayer coatings is proposed. Using the technologically important hard transition metal carbides as prototypes, although the principle is transferable also to other systems, we demonstrate, from first-principles calculations, that by suitable alloying the energy difference between several competing structures in the transition meta[ carbides is small or tunable. This creates multiphase/polytypic compounds with a random or controllable layer stacking sequence, systems in which the propagation of dislocations can be strongly suppressed by a large number of interfaces between structures with different glide systems, accordingly allowing the possibility of a greatly enhanced hardness. With modern thin-film technologies, it should therefore be possible to deposit such materials that will express multilayer characteristics with only minor changes in the chemical constitution of the material, which is in contrast to conventional superlattices.
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| 37. |
- Hugosson, Håkan Wilhelm, 1972-, et al.
(författare)
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Theoretical studies of substitutional impurities in molybdenum carbide
- 1999
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 60:22, s. 15123-15130
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Tidskriftsartikel (refereegranskat)abstract
- First-principles full-potential linear muffin-tin orbital calculations have been used to study the effect on the cohesion and electronic structure of cubic δ-MoC when 25% of the carbon is substituted for boron, nitrogen, or oxygen and when 25% of the molybdenum is substituted for niobium, tungsten, or ruthenium. A thorough study of the changes in the electronic structure and the effect of these on the properties of the compounds is made. Special attention is paid to the character (ionic, covalent, or metallic) of the states becoming occupied (or unoccupied) due to the substitution. A study is also made on the properties of the quaternary alloy Mo0.75W0.25C0.75N0.25. This substitution is shown to harden δ-MoC.
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| 38. |
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| 39. |
- Hugosson, Håkan Wilhelm, 1972-, et al.
(författare)
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Theory of phase stabilities and bonding mechanisms in stoichiometric and substoichiometric molybdenum carbide
- 1999
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 86:7, s. 3758-3767
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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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| 40. |
- Isaev, Eyvaz, et al.
(författare)
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Intrinsic defects and transition metal impurities in GaAs
- 2004
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 272:3, s. 1961-1962
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Tidskriftsartikel (refereegranskat)abstract
- Thermodynamics of intrinsic point defects, 3d-transition metal (TM) impurities, and various defect pairs in GaAs have been studied by means of the locally self-consistent Green's function method. Antisite defects, As-Ga, are found to be the most energetically favorable defects in the As-rich GaAs. The studied TM impurities (V, Cr, Mn, and Fe) are found to form substitutional alloys on the Ga sublattice. The magnetic moments of TM impurities in the GaAs host are calculated under the assumption that orbital moments of TM are quenched and the total magnetization is due to spill ordering of electrons in the crystal. Thermodynamic possibility of formation of complexes between TM-atoms is investigated.
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| 41. |
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| 42. |
- James, P, et al.
(författare)
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Calculated trends of the magnetostriction coefficient of 3d alloys from first principles
- 2000
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Ingår i: APPLIED PHYSICS LETTERS. - : AMER INST PHYSICS. - 0003-6951. ; 76:7, s. 915-917
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Tidskriftsartikel (refereegranskat)abstract
- The general behavior of the magnetostriction coefficients for Fe, Co, and Ni and their alloys is reproduced by first-principles theory. It is shown that the low magnetostriction coefficient of soft magnetic materials, observed for specific alloy concentra
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| 43. |
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| 44. |
- Kádas, Krisztina, et al.
(författare)
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Magnetism-driven anomalous surface alloying between Cu and Cr
- 2009
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 94:17
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Tidskriftsartikel (refereegranskat)abstract
- Cu-Cr contact materials are widely used as medium- and high-voltage vacuum interrupters. The microstructure of these materials is critical in their performance: the finer structure they have, the better are their physical properties. A solid solution of Cu and Cr could significantly increase the performance of such contact materials. However, Cu and Cr are practically immiscible in the bulk phase. Based on first principles density functional theory we show here that the solubility of Cr in Cu is dramatically increased on Cu surfaces already at room temperature and Cu-Cr alloys are formed on both the Cu(111) and Cu(100) surfaces. We demonstrate that the origin of this phenomenon is the unique magnetic properties of Cr atoms near surfaces.
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| 45. |
- Kádas, Krisztina, et al.
(författare)
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Theoretical prediction of the elastic properties of body-centered cubic Fe-Ni-Mg alloys under extreme conditions
- 2012
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Ingår i: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 92:7, s. 888-898
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Tidskriftsartikel (refereegranskat)abstract
- Using density functional theory formulated within the framework of the exact muffin-tin orbital method, we investigate the elastic properties of the body-centered cubic Fe0.85Ni0.1Mg0.05 alloy in the conditions at the Earth's inner core. We demonstrate that in this system, the chemical stabilization effect of Mg is significantly larger than that of Ni. We show that the elastic properties of Fe(0.85)Ni(0.1)Mg(0.0)5 are in good agreement with those of the Earth's inner core, as given by seismic observations. We find that the excellent mechanical properties of Fe0.85Ni0.1Mg0.05 are primarily due to Mg.
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| 46. |
- Kadas, Krisztina, et al.
(författare)
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Thermo-physical properties of body-centered cubic iron-magnesium alloys under extreme conditions
- 2011
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Ingår i: Solid State Communications. - : Elsevier BV. - 0038-1098 .- 1879-2766. ; 151:3, s. 203-207
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Tidskriftsartikel (refereegranskat)abstract
- Using density functional theory formulated within the framework of the exact muffin-tin orbitals method, we investigate the thermo-physical properties of body-centered cubic (bcc) iron-magnesium alloys, containing 5 and 10 atomic % Mg, under extreme conditions, at high pressure and high temperature. The temperature effect is taken into account via the Fermi-Dirac distribution of the electrons. We find that at high pressures pure bcc iron is dynamically unstable at any temperature, having a negative tetragonal shear modulus (C'). Magnesium alloying significantly increases C' of Fe, and bcc Fe-Mg alloys become dynamically stable at high temperature. The electronic structure origin of the stabilization effect of Mg is discussed in detail. We show that the thermo-physical properties of a bcc Fe-Mg alloy with 5% Mg agree well with those of the Earth's inner core as provided by seismic observations. (C) 2010 Elsevier Ltd. All rights reserved.
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| 47. |
- Karis, O, et al.
(författare)
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Probing surface states of Cu/Ni thin films using x-ray absorption spectroscopy
- 2001
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 63:11
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Tidskriftsartikel (refereegranskat)abstract
- Surface and interface properties of Cu thin films (1–4 monolayers) deposited on Ni(100) have been extracted by means of x-ray absorption spectroscopy and analyzed in combination with ab initio density-functional calculations. An unoccupied Cu surface state is identified in an x-ray absorption spectra and studied as a function of film thickness. Experimental data is supported by calculations of the layer-resolved density of states and the results from this combined theoretical-experimental effort show that the surface state is almost entirely located on the atomic layer closest to the vacuum. Our results also indicate strong hybridization between unoccupied states at the Cu/Ni interface boundary.
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| 48. |
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| 49. |
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| 50. |
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