| 1. |
- Schmitt, T, et al.
(författare)
-
Resonant soft X-ray emission spectroscopy of doped and undoped vanadium oxides
- 2004
-
Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 362:1-2, s. 143-150
-
Tidskriftsartikel (refereegranskat)abstract
- Resonant soft X-ray emission (RSXE) spectra of NaV2O5, MoxV1-xO2 and V2O3 have been recorded for a series of excitation energies at resonances of the V L- and O K-absorption band. Resonant excitation allows us, firstly, to separate V 3d and O 2p projected density-of-states of the valence band and, secondly, to study charge-neutral low-energy excitations due to resonant inelastic X-ray scattering (RIXS). We found that both the V L- and the O K-emission spectra clearly show components originating from O 2p- and V 3d-states, reflecting the high degree of hybridization of the valence band in all compounds. At threshold excitation we observed that NaV2O5 spectra are dominated by RIXS whereas MoxV1-xO2 and V2O3 spectra show bandlike features, which may be due to differences in the correlation effects of the compounds. We compared the RSXE spectra with cluster model calculations, which gives a good account for NaV2O5 whereas the RSXE spectra of the other compounds show RIXS only at certain energies well above the threshold. In fact, we interpret the trend in the RSXE spectra of the MoxV1-xO2 compound system as a successive filling of the (rigid) V 3d band with increasing Mo content. (C) 2003 Elsevier B.V. All rights reserved.
|
|
| 2. |
- Edvardsson, Sverker, et al.
(författare)
-
The energy matrix using determinantal product states applied to Ho:YAG
- 2000
-
Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 303-304, s. 280-284
-
Tidskriftsartikel (refereegranskat)abstract
- A program written in C is applied for calculations of energy levels and wavefunctions of the lanthanides or actinides. Standard non-relativistic phenomenological operators are used. Simple determinantal product states are used to form the basis set. The complete energy matrix is diagonalized with all operators interacting simultaneously thus allowing mixing of all quantum numbers. The crystal field splitting can also be studied via the standard crystal field hamiltonian as well as the magnetic field influence on the energy levels. The program is here applied to the technologically interesting trivalent ion holmium which is used to form extremely strong magnets as well as the medical eye-safe laser Ho:YAG. Both experimentally fitted and calculated self-consistent crystal field parameters are used to study the energy structure. Crystal ionic polarizabilities with electron correlation included are partly calculated. Zeeman split levels are also studied.
|
|
| 3. |
|
|
| 4. |
- Godlewski, M., et al.
(författare)
-
Mn2+ intra-shell recombination in bulk and quantum dots of II-VI compounds
- 2002
-
Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 341:1-2
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Origin of a fast component of the photoluminescence (PL) decay of Mn 2+ intra-shell 4T1 ? 6A 1 transition in bulk and quantum dot structures is discussed based on the results of PL, PL kinetics and optically detected magnetic resonance experiments. It is demonstrated that a fast component of the PL decay, reported previously for quantum dot structure and related to quantum confinement effects, is also observed in bulk samples and is very much enhanced upon generation of free carriers. The appearance of this fast component of the PL decay is related to a very efficient spin cross-relaxation between localized spins of Mn ions and spins of free carriers. © 2002 Elsevier Science B.V. All rights reserved.
|
|
| 5. |
- Hillert, M., et al.
(författare)
-
Point defects in B2 compounds
- 2001
-
Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 329:02-jan, s. 208-213
-
Tidskriftsartikel (refereegranskat)abstract
- Point defects in B2 compounds are described with a model based on the formula (A,B,Va),(B,A,Va), and results are compared with previous results from two models based on combined defects and using the formulae (A,B), (B,A), and (A,Va)(1) (B,A)(1) The comparison is straight-forward close to the stoichiometric composition but not closer to the pure elements. Using the more general model, it is demonstrated that the fact that vacancies are the predominant defect in some B2 compounds with a small excess of B atoms depends primarily on interactions between next-nearest neighbours rather than on a high enthalpy of formation of the compound, as proposed earlier.
|
|
| 6. |
- Hillert, Mats
(författare)
-
The compound energy formalism
- 2001
-
Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 320:2, s. 161-176
-
Tidskriftsartikel (refereegranskat)abstract
- The compound energy formalism for solution phases with sublattices is very flexible and thermodynamic models for a large variety of phases have been constructed within this formalism. The range of applications is reviewed and the methods of handling various problems are examined. Recent developments including treatments of short range order within the compound energy formalism are reviewed.
|
|
| 7. |
- Kiros, Yohannes, et al.
(författare)
-
Effect and characterization of dopants to Raney nickel for hydrogen oxidation
- 2003
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 360:02-jan, s. 279-285
-
Tidskriftsartikel (refereegranskat)abstract
- Raney nickel and its alloys with the transition metals were prepared and investigated as gas diffusion electrodes for the hydrogen oxidation reaction (HOR) in 6 M KOH and at 60degreesC. The spongy Raney nickel prepared by a mixture of Ni and Al with a weight ratio of 1: 1 was compared for the catalytic activity as hydrogen electrodes with other alloy formations containing 2 wt.% of Cu, Fe, Cr, Ti and La. Depending on the composition of the active layer, the electrocatalytic activity of the Raney nickel was found to decrease in a descending order of the doped metals: Cr>La>Ti>Cu>Fe and with no admixture. The catalytic response of the electrodes, especially for the Cr and Ti-based Raney Ni showed high enrichment and aggregation on the surface and hence affects the activity and stability. Surface area, particle size. average pore diameter, particle morphology and surface elements of the various alloy combinations, have been analyzed and assessed using BET-specific surface areas, SEM and EDXS.
|
|
| 8. |
|
|
| 9. |
- Lyubimtsev, A. L., et al.
(författare)
-
The structure and bonding of Ni3Sn
- 2002
-
Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 340:02-jan, s. 167-172
-
Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of Ni3Sn was calculated at ab initio levels for the crystal structure of the low-temperature modification of Ni3Sn refined upon data of single-crystal X-ray diffractometry (P6(3)/mmc, a=5.2950(7), c=4.247(1) Angstrom R=0.0288). The calculations were made with the use of fixed Gaussian (CRYSTAL98 software) and energy-dependent (Stuttgart TB-LMTO-ASA software) basis sets. Difference electron charge density maps were analysed and compared with that of a hypothetical hcp Ni in order to understand bonding in Ni3Sn. It was found that bonding in Ni3Sn has multicentre character with Ni-Sn interaction stronger than Ni-Ni one.
|
|
| 10. |
- Mao, Huahai, et al.
(författare)
-
Volumetric properties and phase relations of silica - thermodynamic assessment
- 2001
-
Ingår i: Journal of Alloys and Compounds. - 0925-8388 .- 1873-4669. ; 327:1-2, s. 253-262
-
Tidskriftsartikel (refereegranskat)abstract
- Taking into account various available experimental data, an improved internally consistent data set for the SiO2 system is obtained by thermodynamic assessment. The volumetric properties for SiO2 polymorphs are reassessed using the CALPHAD method. A two-coefficient expression is used to describe the thermal expansion and bulk modulus. For liquid phase, one equation is achieved in the temperature range of 298-4000 K either for thermal expansion or for bulk modulus. Phase diagrams have been calculated up to 40 GPa. It has been concluded that, in the pressure range lower than 20 GPa, there is no significant difference between the phase diagrams calculated by the Birch-Murnaghan equation of state (EOS) and by Murnaghan EOS.
|
|
