uu.seUppsala universitets publikasjoner
Endre søk
Begrens søket
78910 451 - 469 of 469
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Treff pr side
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
  • Standard (Relevans)
  • Forfatter A-Ø
  • Forfatter Ø-A
  • Tittel A-Ø
  • Tittel Ø-A
  • Type publikasjon A-Ø
  • Type publikasjon Ø-A
  • Eldste først
  • Nyeste først
  • Skapad (Eldste først)
  • Skapad (Nyeste først)
  • Senast uppdaterad (Eldste først)
  • Senast uppdaterad (Nyeste først)
  • Disputationsdatum (tidligste først)
  • Disputationsdatum (siste først)
Merk
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 451. Yang, X
    et al.
    Riseborough, S
    Durakiewicz, T
    Olson, G
    Joyce, J
    Bauer, D
    Sarrao, L
    Moore, P
    Graham, S
    Elgazzar, S
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Oppeneer, Peter M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Guziewicz, E
    Butterfield, T
    Unusual quasiparticle renormalizations from angle resolved photoemission on USb22009Inngår i: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 89, nr 22-24, s. 1893-1911Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Angle-resolved photoemission experiments have been performed on USb2, and very narrow quasiparticle peaks have been observed in a band, which local spin-density approximation (LSDA) predicts to osculate the Fermi energy. The observed band is found to be depressed by 17 meV below the Fermi energy. Furthermore, the inferred quasiparticle dispersion relation for this band exhibits a kink at an energy of about 23 meV below the Fermi energy. The kink is not found in LSDA calculations and, therefore, is attributable to a change in the quasiparticle mass renormalization by a factor of approximately 2. The existence of a kink in the quasiparticle dispersion relation of a band that does not cross the Fermi energy is unprecedented. The kink in the quasiparticle dispersion relation is attributed to the effect of the interband self-energy, involving transitions from the osculating band into a band that does cross the Fermi energy.

  • 452. Yu, Shun
    et al.
    Ahmadi, Sarch
    Palmgren, Pål
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi.
    Hennies, Franz
    Zuleta, Marcelo
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för fysikalisk och analytisk kemi. Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Gothelid, Mats
    Modification of charge transfer and energy level alignment at organic/TiO2 interfaces2009Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, nr 31, s. 13765-13771Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Adsorption of titanyl phthalocyanine (TiOPc) on rutile TiO2(110) modified by a set of pyridine derivatives (2,2'-bipyridine, 4,4'-bipyridine, and 4-tert-butyl pyridine) has been investigated using synchrotron radiation based X-ray photoelectron spectroscopy (XPS). For the unmodified TiOPc/TiO2 system, a strong charge transfer is observed from the first layer TiOPc into the substrate, which leads to a molecular layer at the interface with a depleted highest occupied molecular orbital (HOMO). However, precovering the TiO2 surface with a saturated pyridine monolayer effectively reduce this process and leave the TiOPc in a less perturbed molecular state. Furthermore, the TiOPc HOMO and core levels are observed at different binding energies ranging by 0.3 eV on the three pyridine monolayers, which is ascribed to differences in surface potentials set up by the different pyridine/TiO2 systems.

  • 453.
    Yun, Younsuk
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Eriksson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Oppeneer, Peter M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    First-principles modeling of He-clusters in UO22009Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 385, nr 1, s. 72-74Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated the behavior of He in UO2, Using the projector-augmented-wave (PAW) method and the generalized gradient approximation (GGA) based on the density functional theory. Total energy calculations with atomic relaxation included have been performed in a 96-atom large supercell. We have found that He has a strong tendency to form a cluster in vicinity of an octahedral interstitial site (OIS) in the UO2 matrix. In addition, the strain energy produced by a He-cluster was found to be sufficient to create point defects of the host atoms in UO2. Our study suggests that He-clusters and He-induced point defects play an important role for the local mechanical properties Of UO2 (C) 2008 Elsevier B.V. All rights reserved.

  • 454.
    Yun, Younsuk
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Eriksson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Oppeneer, Peter M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Theory of He trapping, diffusion, and clustering in UO22009Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 385, nr 3, s. 510-516Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have performed ab initio total energy calculations to investigate the behavior of helium and its diffusion properties in uranium dioxide MOD. Our investigations are based on the density functional theory within the generalized gradient approximation (GGA). The trapping behavior of He in UO2 has been modeled with a supercell containing 96-atoms as well as uranium and oxygen vacancy trapping sites. The calculated incorporation energies show that for He a uranium vacancy is more stable than an oxygen vacancy or an octahedral interstitial site (OIS). Interstitial site hopping is found to be the rate-determining mechanism of the He diffusion process and the corresponding migration energy is computed as 2.79 eV at 0 K (with the spin-orbit coupling (SOC) included), and as 2.09 eV by using the thermally expanded lattice parameter of UO2 at 1200 K, which is relatively close to the experimental value of 2.0 eV. The lattice expansion coefficient of He-induced swelling of UO2 is calculated as 9 x 10(-2). For two He atoms, we have found that they form a dumbbell configuration if they are close enough to each other, and that the lattice expansion induced by a dumbbell is larger than by two distant interstitial He atoms. The clustering tendency of He has been studied for small clusters of up to six He atoms. We find that He strongly tends to cluster in the vicinity of an OIS, and that the collective action of the He atoms is sufficient to spontaneously create additional point defects around the He cluster in the UO2 lattice. (C) 2008 Elsevier B.V. All rights reserved.

  • 455.
    Yun, Younsuk
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Eriksson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Oppeneer, Peter M.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Kim, Hanchul
    Park, Kwangheon
    First-principles theory for helium and xenon diffusion in uranium dioxide2009Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 385, nr 2, s. 364-367Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The diffusion properties of He and Xe in UO2 have been investigated, using density-functional calculations employing the projector-augmented-wave (PAW) method and the generalized gradient approximation (GGA). The migration energies corresponding to both interstitial and vacancy-assisted mechanisms have been calculated and the results for the two noble gas atoms are compared with each other. We suggest that He likely diffuses by hopping through a single vacancy with computed low migration energies smaller than 0.79 eV and its diffusivity is much higher than that of Xe. Xe has a quite large migration energy compared to He; the strain energy plays a key role in Xe diffusion in UO2.

  • 456.
    Yun, Younsuk
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Kim, Hanchul
    Kim, Heemoon
    Park, Kwangheon
    Atomic diffusion mechanism of Xe in UO22008Inngår i: Journal of Nuclear Materials, ISSN 0022-3115, E-ISSN 1873-4820, Vol. 378, nr 1, s. 40-44Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have investigated vacancy-assisted diffusion of Xe in uranium dioxide MOO calculating incorporation, binding, and migration energies. All the energy values have been obtained using the density functional theory (DFT) within the generalized gradient approximation (GGA) and the projector-augmented-wave (PAW) method. Considering spin-polarization effect, we find that the computed migration energy is reduced by and agrees well with experimental data compared to those obtained from nonmagnetic calculations. We also find that an oxygen vacancy lowers the migration energy of a uranium vacancy by about 1 eV, enhancing an effective movement of vacancy clusters consisting of both uranium and oxygen vacancies. Furthermore, the strain energy of Xe is large enough to contribute to the clustering of vacancies making it the driving force for the vacancy-assisted diffusion of Xe in UO2. In summary all the calculated results suggest that the trivacancy is a major diffusion pathway of Xe in UO2.

  • 457.
    Yun, Younsuk
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Oppeneer, Peter M.
    Kim, Hanchul
    Park, Kwangheon
    Defect energetics and Xe diffusion in UO2 and ThO22009Inngår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 57, nr 5, s. 1655-1659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We have performed ab initio total energy calculations to investigate the defect energetics and diffusion behavior of Xe in UO2 and ThO2 matrices. All calculations have been carried out Using density functional theory within the generalized gradient approximation and applying the projector-augmented-wave method. Our results Show that the formation and migration energies of vacancy defects are more than twice as high in ThO2 compared with UO2. Another notable difference between the two oxides is the role played by an oxygen vacancy ill the movement of a cation vacancy. An vacancy enhances the movement Of a uranium vacancy by lowering its migration energy by about 1 eV, but a similar effect is not observed in ThO2. The different behavior of cation vacancies in the two oxides strongly affects the mobility of fission gases and leads to differences in their respective diffusion behavior. We sui, est that the strong resistance against oxidation of ThO2 prevents the creation and migration of defects. and results ill a lower mobility of fission gases ill ThO2 as compared to UO2.

  • 458. Zeng, Qiao-Shi
    et al.
    Ding, Yang
    Mao, Wendy L
    Luo, Wei
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Blomqvist, Andreas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Yang, Wenge
    Shu, Jinfu
    Sinogeikin, Stas V
    Meng, Yue
    Brewe, Dale L
    Jiang, Jian-Zhong
    Mao, Ho-Kwang
    Substitutional alloy of Ce and Al2009Inngår i: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 106, nr 8, s. 2515-2518Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The formation of substitutional alloys has been restricted to elements with similar atomic radii and electronegativity. Using high-pressure at 298 K, we synthesized a face-centered cubic disordered alloy of highly dissimilar elements (large Ce and small Al atoms) by compressing the Ce(3)Al intermetallic compound >15 GPa or the Ce(3)Al metallic glass >25 GPa. Synchrotron X-ray diffraction, Ce L(3)-edge absorption spectroscopy, and ab initio calculations revealed that the pressure-induced Kondo volume collapse and 4f electron delocalization of Ce reduced the differences between Ce and Al and brought them within the Hume-Rothery (HR) limit for substitutional alloying. The alloy remained after complete release of pressure, which was also accompanied by the transformation of Ce back to its ambient 4f electron localized state and reversal of the Kondo volume collapse, resulting in a non-HR alloy at ambient conditions.

  • 459. Zhan, Yiqiang
    et al.
    Holmstrom, Erik
    Lizarraga, Raquel
    Eriksson, Olle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Liu, Xianjie
    Li, Fenghong
    Carlegrim, Elin
    Stafstrom, Sven
    Fahlman, Mats
    Efficient Spin Injection Through Exchange Coupling at Organic Semiconductor/Ferromagnet Heterojunctions2010Inngår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 22, nr 14, s. 1626-1630Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The schematic visualization of the Alq(3) molecule on the Fe substrate with the optimized geometry at lowest total energy. When the Alq(3) molecule is relaxed on the surface, only two of the wings are lying down on the Fe surface, and the third wing remains perpendicular to the surface, showing a strong hybridization occurance.

  • 460. Zhang, Hualei
    et al.
    Johansson, Börje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Ab initio calculations of elastic properties of bcc Fe-Mg and Fe-Cr random alloys2009Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, nr 22, s. 224201-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the ab initio exact muffin-tin orbitals method in combination with the coherent-potential approximation, we have calculated the elastic parameters of ferromagnetic Fe1-mMgm (0 < m < 0.1) and Fe1-cCrc (0 < c < 0.2) random alloys in the body-centered cubic (bcc) crystallographic phase. Results obtained for Fe1-cCrc demonstrate that the employed theoretical approach accurately describes the experimentally observed composition dependence of the polycrystalline elastic moduli of Fe-rich alloys encompassing maximum similar to 10% Cr. The elastic parameters of Fe-Cr alloys are found to exhibit anomalous composition dependence around 5% Cr. The immiscibility between Fe and Mg at ambient conditions is well reproduced by the present theory. The calculated lattice parameter for the Fe-Mg regular solid solution increases by similar to 1.95% when 10% Mg is introduced in Fe, which corresponds approximately to 11% decrease in the average alloy density, in perfect agreement with the experimental finding. At the same time, we find that all of the elastic parameters of bcc Fe-Mg alloys decrease almost linearly with increasing Mg content. The present results show a much stronger alloying effect for Mg on the elastic properties of alpha-Fe than that for Cr. Our results call for further experimental studies on the mechanical properties of the Fe-Mg system.

  • 461. Zhang, Hualei
    et al.
    Punkkinen, M. P. J.
    Johansson, Börje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Hertzman, Staffan
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Single-crystal elastic constants of ferromagnetic bcc Fe-based random alloys from first-principles theory2010Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, nr 18, s. 184105-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The elastic properties of ferromagnetic Fe1-xMx (M=Al, Si, V, Cr, Mn, Co, Ni, and Rh; 0 <= x <= 0.1) random alloys in the body-centered-cubic (bcc) crystallographic phase have been studied using the all-electron exact muffin-tin orbitals method in combination with the coherent-potential approximation. The theoretical lattice parameters and the single-crystal elastic constants agree well with the available experimental data. The most significant alloying effects are found for Al, Si, and Ni additions. All elements enlarge the lattice parameter and decrease the C-11, C-12, and C' elastic constants and the bulk modulus of bcc Fe. At the same time, C-44 is found to increase with Al, Si, V, Cr, or Mn and remain nearly constant with Co, Ni, and Rh. Accordingly, the elastic anisotropy of bcc Fe increases with all alloying elements considered here. The calculated alloying effects on the single-crystal elastic constants are shown to originate from volume effects in combination with the peculiar electronic structure of bcc Fe.

  • 462. Zhang, Hualei
    et al.
    Punkkinen, Marko P. J.
    Johansson, Börje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Theoretical elastic moduli of ferromagnetic bcc Fe alloys2010Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 22, nr 27, s. 275402-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The polycrystalline elastic parameters of ferromagnetic Fe1-xMx (M = Al, Si, V, Cr, Mn, Co, Ni, Rh; 0 <= x <= 0.1) random alloys in the body centered cubic (bcc) crystallographic phase have been calculated using first-principles alloy theory in combination with statistical averaging methods. With a few exceptions, the agreement between the calculated and the available experimental data for the polycrystalline aggregates is satisfactory. All additions considered here decrease the bulk modulus (B) and Poisson's ratio (nu) of bcc Fe. The complex composition dependence of the C-44 single-crystal elastic constant is reflected in the polycrystalline shear modulus (G), Young's modulus (E), and Debye temperature (Theta). The polycrystalline anisotropy of bcc Fe is increased by all additions, and Al, Si, Ni, and Rh yield the largest alloying effects.

  • 463.
    Zhonglai, Li
    et al.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    Larsson, J. Andreas
    Tyndall National Institute, University College Cork.
    Larsson, Peter
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Tobin, Joseph M.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    O'Byrne, Justin
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    Morris, Michael A.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    Attard, Gary
    School of Chemistry, Cardiff University.
    Holmes, Justin D.
    Department of Chemistry, Materials Section and Supercritical Fluid Centre, University College Cork.
    Copper/Molybdenum Nanocomposite Particles as Catalysts for the Growth of Bamboo-Structured Carbon Nanotubes2008Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 32, s. 12201-12206Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Bamboo-structured carbon nanotubes (BCNTs), with mean diameters of 20 nm, have been synthesized on MgO-supported Cu and Mo catalysts by the catalytic chemical vapor deposition of methane. BCNTs could only be generated using a combination of Cu and Mo catalysts. No BCNTs were produced from either individual Cu or Mo catalysts. In combination, Mo was found to be essential for cracking the methane precursor, while Cu was required for BCNT formation. Energy dispersive X-ray analysis of the individual particles at the tips of the nanotubes suggest that Cu and Mo are present as a “composite” nanoparticle catalyst after growth. First-principles modeling has been used to describe the interaction of the Cu/Mo catalyst with the nanotubes, suggesting that the catalyst binds with the same energy as traditional catalysts such as Fe, Ni, and Co.

  • 464. Zhou, Jian
    et al.
    Sun, Zhimei
    Xu, Lihua
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Effect of dopants on the structure and properties of Ge2Sb2Te5 studied by Ab initio calculations2008Inngår i: Solid State Communications, ISSN 0038-1098, E-ISSN 1879-2766, Vol. 148, nr 3-4, s. 113-116Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Ge2Sb2Te5 is technologically important for phase-change random access memory applications. In this work, the effect of doping Ag, Cd, in and Sn on the structure and chemical bonding of Ge2Sb2Te5 has been studied by ab initio calculations. It has been shown that the 3.7 at.% dopants drastically weaken the Te-Te bond strength in the -Te-(vacancy)-Te- configuration while maintaining its rocksalt symmetry. According to the analysis of formation energy, doping at the Ge site of Ge2Sb2Te5 phase is more favourable. The doped Ge2Sb2Te5 phases demonstrate either semiconductor or metallic behavior, which is attributed to the valence electrons of the dopants that mainly contribute to either the conductivity or chemical bonding.

  • 465. Zolyomi, V.
    et al.
    Kollar, J.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Anomalous surface relaxation in hcp transition metals2008Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, nr 19, s. 195414-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-principles total-energy calculations indicate anomalously large surface relaxations for groups IVA and VIIA hcp metals. In addition, for group VIIA elements the magnitude of the layer relaxation exhibits an unusually slow decay with the distance from the surface. We argue that the above phenomena can be traced back to the peculiar Fermi surface of groups IVA and VIIA hcp metals. Namely, the anomalous surface relaxation appears as a consequence of low-energy excitations with near 2k(F) wave vectors, which is also reflected by the flat and degenerate d bands located close to the Fermi level in the L-A-H plane of the hcp Brillouin zone.

  • 466. Zolyomi, V.
    et al.
    Kollar, J.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    On the surface relaxation of transition metals2008Inngår i: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 88, nr 18-20, s. 2709-2714Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First principles band structure calculations are presented for the layer relaxation of the close-packed surfaces of 5d transition metals. Anomalously large relaxations are found for group IVA and VIIA hcp metals. For these elements, the size of the layer relaxation exhibits an unusually slow decay with the distance from the surface. We argue that this phenomenon can be attributed to the peculiar flat and degenerate d-bands located close to the Fermi level in the L-A-H top-plane of the hcp Brillouin zone, and which are also responsible for the anomalously low [001] longitudinal optical phonon frequencies observed in these hcp metals.

  • 467. Zolyomi, V
    et al.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Materialteori.
    Kwon, S. K.
    Kollar, J
    Surface relaxation and stress for 5d transition metals2009Inngår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 21, nr 9, s. 095007-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Using the density functional theory, we present a systematic theoretical study of the layer relaxation and surface stress of 5d transition metals. Our calculations predict layer contractions for all surfaces, except for the ( 111) surface of face centered cubic Pt and Au, where slight expansions are obtained similarly to the case of the 4d series. We also find that the relaxations of the close packed surfaces decrease with increasing occupation number through the 5d series. The surface stress for the relaxed, most closely packed surfaces shows similar atomic number dependence as the surface energy. Using Cammarata's model and our calculated surface stress and surface energy values, we examine the possibility of surface reconstructions, which is in reasonable agreement with the experimental observations.

  • 468.
    Åhlund, John
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Nilsson, Katarina
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Palmgren, Pål
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Göthelid, Emmanuelle
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Schiessling, J.
    Göthelid, M.
    Mårtensson, Nils
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Puglia, Carla
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap, Yt- och gränsskiktsvetenskap.
    Molecular growth determined by surface domain patterns2008Inngår i: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 112, nr 17, s. 6887-6890Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The growth of iron phthalocyanine (FePc) on InSb(001) c(8 × 2) at submonolayer coverage has been investigated with scanning tunneling microscopy (STM). FePc adsorbs flat centered on the In rows both at 70 K and at room temperature (RT). However, the shapes of the two-dimensional molecular islands are fundamentally different; while the RT growth results in chainlike structures along the [110] direction, as already observed for other Pc's adsorbed on the same surface, the islands are prolonged along [10], i.e., perpendicular to the substrate rows, at 70 K. These observations are explained on the basis of a recently observed new surface phase at low temperature, resulting in structural domains on the surface. The molecular growth front follows the propagating domain boundary that freezes at low temperature.

  • 469. Öhrwall, G.
    et al.
    Tchaplyguine, M.
    Marburger, S.
    Hergenhahn, U.
    Svensson, S.
    Björneholm, O.
    Lundwall, M.
    Feifel, R.
    Bergersen, H.
    Rander, T.
    Lindblad, A.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och materialvetenskap.
    Schulz, J.
    Peredkov, S.
    Barth, S.
    Femtosecond interatomic coulombic decay in free neon clusters: Large lifetime differences between surface and bulk2005Inngår i: Physical Review Letters, ISSN 0031-9007, Vol. 93, nr 17, s. 173401-Artikkel i tidsskrift (Fagfellevurdert)
78910 451 - 469 of 469
RefereraExporteraLink til resultatlisten
Permanent link
Referera
Referensformat
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Annet format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annet språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf