| 1. |
- Bangert, U., et al.
(author)
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Electron energy loss spectroscopic studies of brown diamonds
- 2006
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 86:29-31, s. 4757-4779
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Journal article (peer-reviewed)abstract
- We investigate both experimentally and theoretically, low-loss electron energy losses in brown type IIa monocrystalline diamonds both before and after high-temperature, high-pressure anneals which remove the brown colouration. We find additional losses within and near the band edge for brown diamond which are significantly reduced after treatment. The additional losses are not associated with dislocations. Graphitic inclusions are detected by EELS as well as TEM studies for some brown diamonds before treatment. These lead to pronounced subgap absorption. However, all brown diamonds exhibit additional losses which are due to point defects lying in the regions between dislocations. First principles theoretical modelling shows that common dislocations are not responsible for the brown colouration but a -bonded vacancy disk lying on {111} planes gives broad bands lying in the diamond band gap, possesses an optical absorption spectrum similar to that of brown diamond, and leads to additional electron energy losses in the band edge region. These and similar defects are suggested to be responsible for the brown colouration. Mechanisms are proposed for their formation and removal.
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| 2. |
- Carini, Giovanni, et al.
(author)
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Ultrasonic and hypersonic behaviours of borate glasses
- 2007
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In: Philosophical Magazine. - 1478-6435 .- 1478-6443. ; 87, s. 697-703
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Journal article (peer-reviewed)abstract
- Comparative measurements of Brillouin light scattering and ultrasound in (K2O)0.04(B2O3)0.96 and (Ag2O)0.14(B2O3)0.86 borate glasses as a function of temperature between 1.5 and 300 K reveal that distinct mechanisms regulate the temperature behaviours of the acoustic attenuation. In the MHz range the attenuation and the sound velocity are mainly governed by (i) quantum-mechanical tunnelling below 20 K, (ii) thermally activated relaxations between 20 and 200 K and (iii) vibrational inharmonicity at even higher temperatures. In the GHz range and in the temperature interval between 77 and 300 K, additional contributions besides the relaxation process must be taken into consideration to account for the hypersonic attenuation.
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| 3. |
- Chen, G., et al.
(author)
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Protein fluctuations explored by inelastic neutron scattering and dielectric relaxation spectroscopy
- 2008
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 88:33-35, s. 3877-3883
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Conference paper (peer-reviewed)abstract
- Glasses, supercooled liquids and proteins share common properties, in particular the existence of an energy landscape and the presence of two types of fluctuations, alpha and beta. While the effect of alpha fluctuations on proteins has been known for a few years, the effect of beta fluctuations has not been fully understood. By comparing neutron-scattering data on the protein myoglobin with beta fluctuations in the hydration shell measured by dielectric relaxation spectroscopy, we show that the internal protein motions are slaved to these fluctuations. We also show that there is no 'dynamical transition' in proteins near 200 K. The rapid increase in the mean-square displacement with temperature in many neutron-scattering experiments can be quantitatively predicted by beta fluctuations in the hydration shell.
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| 4. |
- Dahlberg, Carl F. O., et al.
(author)
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Hardening and softening mechanisms at decreasing microstructural length scales
- 2008
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 88:30-32, s. 3513-3525
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Journal article (peer-reviewed)abstract
- A laminate structure with varying lamina thicknesses is used as a qualitative model of grain size dependence on yield behaviour in metallic materials. Both strain gradient plasticity and slip between layers are considered. It is shown that an inverse Hall-Petch effect can be generated in this way. For very small thicknesses, corresponding to very small grain sizes, sliding is the dominant mechanism and the strength then decreases with decreasing thickness. For larger thicknesses, strain gradient plasticity is controlling the deformation and the strength is, instead, increasing with decreasing thickness. Numerical examples are presented that demonstrate these mechanisms.
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| 5. |
- Dupin, N., et al.
(author)
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Using first-principles results to calculate finite-temperature thermodynamic properties of the Nb-Ni mu phase in the Bragg-Williams approximation
- 2006
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 86:12, s. 1631-1641
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Journal article (peer-reviewed)abstract
- Results of first-principles (FP) total energy calculations for 32 different configurations of the mu phase in the binary system Nb-Ni are used in the compound energy formalism (CEF) to model finite-temperature thermodynamic properties. A comparison with Cluster Expansion Hamiltonian-Cluster Variation Method (CEH-CVM) calculations indicates that the CEF describes temperature-dependent site occupancies as well as the CEH-CVM within the temperature range of interest for applications. This suggests that the Bragg-Williams-Gorsky approximation (BWGA) used in the CEF is sufficient to describe site occupancies and thermodynamics of the mu phase. A phase diagram is calculated using the mu phase description derived in the present work together with a previous Calphad description for the other phases of this system. The FP-CEF approach significantly improves the description of the thermodynamic properties as a function of composition compared to the Calphad procedure generally used up to now.
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| 6. |
- Etz, Corina, et al.
(author)
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ROTMOKE : An assessment of macroscopic models for bcc Ni/Ni(100)
- 2008
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 88:18-20, s. 2765-2775
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Journal article (peer-reviewed)abstract
- Ab-initio Kerr angles for a multilayer system were calculated by means of Luttinger's formalism within the spin-polarized relativistic screened Korringa-Kohn-Rostoker method by including all multiple reflections and optical interferences via the 2 2 matrix technique. Two further macroscopic models are suggested for a multilayer system; i.e., the two-media approach and the three-media approach. The Kerr angles obtained using the two-media approach show that 75 % of the Kerr rotation angles arise from surface contributions when compared to the 2 2 matrix approach. Furthermore, by comparing the three-media approach to the 2 2 matrix technique it is found that almost 25 % of the Kerr rotation angles are due to interfaces between the atomic layers
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| 7. |
- Hepburn, D. J., et al.
(author)
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Rescaled potentials for transition metal solutes in α-iron
- 2009
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 89, s. 3393-3411
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Journal article (peer-reviewed)abstract
- We present semi-empirical potentials for dilute transition metal solutes in α-iron. They are in the Finnis–Sinclair form and are therefore suitable for billion atom molecular dynamics simulations. The potentials have been developed using a rescaling technique to provide solute–iron and solute–solute interactions from an existing iron potential. By fitting to first principles calculations, which show clear trends in the properties of transition metal solutes in iron across the series, we find trends in the rescaling parameters, which we model using simple functions of the occupancy of the d-electron band. We comment on the possibility of utilizing such relationships for the fundamental electronic properties of the solute to create multicomponent potentials for transition metal solutes in α-iron.
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| 8. |
- Johansson, Börje, et al.
(author)
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Itinerant f-electron elements
- 2009
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 89:22-24, s. 1793-1799
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Journal article (peer-reviewed)abstract
- To obtain a proper understanding of the 5f elements, the actinides, it is useful to compare their behavior with the 4f transition elements, the lanthanides. It is especially rewarding to capitalize on the remarkable similarity between the solid-state properties of compressed Ce and the actinide metals. The intensively studied alpha-gamma transition in Ce is considered to be a Mott transition, namely, the 4f electron changes its behavior from being localized to become delocalized (itinerant/metallic). This change also means that the 4f electron transforms from a non-bonding to a bonding configuration which, in turn, gives rise to a volume collapse. This collapse is isostructural in character, which contributes to the immense interest in this phase transition. An analogous and remarkable change in bonding (cohesive) properties is also found within the actinide series, where the sudden volume increase from Pu to Am (50%) can be viewed as a Mott transition within the 5f shell as a function of atomic number Z. The elements on the metallic side of the 5f Mott transition, i.e. the earlier actinides (Pa-Pu), show low symmetry structures at ambient conditions, while the heavier elements (from Am and beyond) adopt structures typical for the lighter trivalent lanthanide elements with localized 4f electrons. An important consequence of the localized and trivalent behavior in Am is a non-magnetic 5f(6) (J = L + S = 0) configuration for the f electrons. This led to the prediction of superconductivity in americium and subsequently to its experimental verification.
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| 9. |
- Larsson, Per-Lennart
(author)
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Modelling of sharp indentation experiments : some fundamental issues
- 2006
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 86:33-35, s. 5155-5177
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Journal article (peer-reviewed)abstract
- Correct interpretation of sharp indentation experiments requires a fundamental understanding of the mechanics involved in the process. Such an understanding can only be achieved if an appropriate mechanical model is used to describe the problem. These models can, in rare cases, be purely analytical, but nowadays numerical modelling is a vital part of the mechanical approach. Furthermore, with the development of new materials and nanoindentation devices, material ( constitutive) modelling has becomes very important. The aim of the present paper is to present an overview of the modelling of sharp indentation experiments. Indentation of classical Mises elastoplastic behaviour, in particular, will be considered, in addition to indentation modelling of other types of materials. In addition, some fundamental issues in indentation modelling will be discussed. These issues include (1) the influence from large deformations, (2) differences and similarities between cone and pyramid indentation results, (3) the influence of residual stresses, (4) the effective elastic modulus at indentation and (5) the differences and similarities between indentation and scratch results. Most of these results have been published previously in international journals but their implications, in the author's opinion, have not been fully appreciated by the indentation community or, at least, not debated sufficiently.
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| 10. |
- Lashley, Jason, et al.
(author)
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A tribute to James L. Smith Foreword
- 2009
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 89:22-24, s. 1751-1756
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Journal article (peer-reviewed)
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| 11. |
- Lundow, Per Håkan, et al.
(author)
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The Ising model for the bcc, fcc and diamond lattices : A comparison
- 2009
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 89:22-24, s. 2009-2042
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Journal article (peer-reviewed)abstract
- A large-scale Monte Carlo simulation study of the Ising model for the simple cubic lattice was recently performed by us. In this paper, we complement that study with the bcc, fcc and diamond lattices. Both the canonical and microcanonical ensembles are employed. We give estimates of the critical temperature and also other quantities in the critical region. An analysis of the critical behaviour points to distinct high-and low-temperature exponents, especially for the specific heat, as was also obtained for the simple cubic lattice, although the agreement is good between the different lattices. The source of this discrepancy is briefly discussed.
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| 12. |
- Massih, Ali R
(author)
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Diffusion-controlled phase growth on dislocations
- 2009
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 89:33, s. 3075-3086
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Journal article (peer-reviewed)abstract
- We treat the problem of diffusion of solute atoms around screw dislocations. In particular, we express and solve the diffusion equation, in radial symmetry, in an elastic field of a screw dislocation subject to the flux conservation boundary condition at the interface of a new phase. We consider an incoherent second-phase precipitate growing under the action of the stress field of a screw dislocation. The second-phase growth rate as a function of the supersaturation and a strain energy parameter is evaluated in spatial dimensions d=2 and d=3. Our calculations show that an increase in the amplitude of dislocation force, e.g. the magnitude of the Burgers vector, enhances the second-phase growth in an alloy. Moreover, a relationship linking the supersaturation to the precipitate size in the presence of the elastic field of dislocation is calculated.
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| 13. |
- Oleynikov, Peter, et al.
(author)
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Structure of the pseudodecagonal Al–Co–Ni approximant PD4
- 2006
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In: Philosophical Magazine. - : Taylor and Francis. - 1478-6435 .- 1478-6443. ; 86:3-5, s. 457-462
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Journal article (peer-reviewed)abstract
- A model for the pseudodecagonal approximant PD4 in the Al–Co–Ni system was deduced from single crystal X-ray diffraction data. The space group is Bbmm with a ?=?101.3, b ?=?32.1 and c ?=?4.1?Å. Atomic positions of 133 unique atoms in the unit cell with a reasonable geometry were found by direct methods and the difference Fourier syntheses. The obtained structure model is in good agreement with high-resolution electron microscopy images of PD4. Diffuse scattering observed along the a * direction in the hkl layers with l ?=?1/2, 3/2 etc. indicates a superstructure with a doubling of the periodicity along the c -axis and a lamellar disorder along the a -axis. If this diffuse scattering is taken into account, c ?=?8.2?Å.
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| 14. |
- Rapp, Östen, et al.
(author)
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Recent results at the metal-insulator transition of icosahedral AIPdRe
- 2006
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 86:05-mar, s. 655-661
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Journal article (peer-reviewed)abstract
- The metal-insulator transition, MIT, in icosahedral AlPdRe has been studied from measurements of magnetoresistance and conductivity. Results for the localisation length xi, the characteristic hopping temperature To and their relations at the MIT are discussed. The results indicate important similarities between i-AlPdRe and doped semiconductors.
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| 15. |
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| 16. |
- Thorning, Casper, et al.
(author)
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Grain boundary ridge formation during initial high temperature oxidation of Mn/Al TRIP steel
- 2007
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 87:23, s. 3479-3499
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Journal article (peer-reviewed)abstract
- Confocal scanning laser microscopy (CSLM) was used in real-time observation of alloy element oxidation of a Mn/Al TRIP steel in an Ar-O-2 atmosphere. CSLM images reveal a marked role of grain boundaries in the overall initial oxidation kinetics of the alloy, and consequently in the morphology of the initial surface oxide. The oxidation on the alloy surface is dominated by the formation of Mn-rich oxide ridges along grain boundary traces on the surface. Oxide ridge formation kinetics was quantified by measurements on images extracted from real-time recordings of surface oxide evolution. Oxide ridge growth was found to take place at a constant rate. Scanning electron microscopy (SEM) images of the oxidized surfaces showed homogenous oxide ridges along straight grain boundary traces and heterogeneous oxide ridges along non-straight grain boundary traces. A transport mechanism of Mn to the surface is proposed, which relies on grain boundary segregation of Mn and on a relationship between grain boundary diffusivity and grain boundary character. It is suggested that when regarding alloys with significant grain boundary segregation of a solute, separate Wagner balances for internal vs. external oxidation is required for the grain lattices and the grain boundaries, respectively.
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| 17. |
- Yang, X, et al.
(author)
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Unusual quasiparticle renormalizations from angle resolved photoemission on USb2
- 2009
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 89:22-24, s. 1893-1911
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Journal article (peer-reviewed)abstract
- 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.
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| 18. |
- Zhang, H., et al.
(author)
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Structure relations in real and reciprocal space of hexagonal phases related to i-ZnMgRE quasicrystals
- 2006
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In: Philosophical Magazine. - : Taylor and Francis Ltd. - 1478-6435 .- 1478-6443. ; 86:3-5, s. 343-348
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Journal article (peer-reviewed)abstract
- The µ 3 , µ 5 and µ 7 approximants in Mg-Zn-RE were related in real and reciprocal space. The structure factors of µ 3 , µ 5 and µ 7 have quite similar intensity distributions and identical phases for the strongest corresponding reflections. Structure models of any of µ 3 , µ 5 and µ 7 can be obtained from any of the others using the strong reflections approach.
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| 19. |
- Zolyomi, V., et al.
(author)
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On the surface relaxation of transition metals
- 2008
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In: Philosophical Magazine. - : Informa UK Limited. - 1478-6435 .- 1478-6443. ; 88:18-20, s. 2709-2714
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Journal article (peer-reviewed)abstract
- 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.
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| 20. |
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