| 1. |
- Ahuja, Rajeev, et al.
(författare)
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High-pressure structural transitions in Cm and Am0.5Cm0.5 binary alloy
- 2006
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 26:4, s. 377-381
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Tidskriftsartikel (refereegranskat)abstract
- The high-pressure behaviour of Cm and Am0.5Cm0.5 binary alloy is investigated theoretically using ab initio electronic structure methods. Our calculations reproduce the structural phase transitions, which are observed in recent experiment performed by Heathman et al. [S. Heathman, R.G. Haire, I Le Bihan et al., Science 309 110 (2005)] and Lindbaum et al. [A. Lindbaum, S. Heathman, T. Le Bihan et al., J. Phys: Condens. Matter 15 S2297 (2003)]. Calculated transition pressures are in reasonable agreement with the experimental values. Calculations performed for an antiferromagnetic state are essential to reproduce the stability of Cm-III phase.
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| 2. |
- Andrault, D, et al.
(författare)
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Study of partial melting at high-pressure using in situ X-ray diffraction
- 2006
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 26:3, s. 267-276
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Tidskriftsartikel (refereegranskat)abstract
- The high-pressure melting behavior of different iron alloys was investigated using the classical synchrotron-based in situ X-ray diffraction techniques. As they offer specific advantages and disadvantages, both energy-dispersive (EDX) and angle-dispersive (ADX) X-ray diffraction methods were performed at the BL04B1 beamline of SPring8 (Japan) and at the ID27-30 beamline of the ESRF (France), respectively. High-pressure vessels and pressure ranges investigated include the Paris- Edinburgh press from 2 to 17GPa, the SPEED-1500 multi-anvil press from 10 to 27 GPa, and the laser-heated diamond anvil cell from 15 to 60 GPa. The onset of melting (at the solidus or eutectic temperature) can be easily detected using EDX because the grains start to rotate relative to the X-ray beam, which provokes rapid and drastic changes with time of the peak growth rate. Then, the degree of melting can be determined, using both EDX and ADX, from the intensity of diffuse X-ray scattering characteristic of the liquid phase. This diffuse contribution can be easily differentiated from the Compton diffusion of the pressure medium because they have different shapes in the diffraction patterns. Information about the composition and/or about the structure of the liquid phase can then be extracted from the shape of the diffuse X-ray scattering.
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| 3. |
- Dubrovinskaia, N., et al.
(författare)
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Compressibility of boron-doped diamond
- 2006
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 26, No. 2, s. 79-85
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Tidskriftsartikel (refereegranskat)
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| 4. |
- Mattesini, M, et al.
(författare)
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An ab initio study of S-substituted iron-nickel-silicon alloy at the Earth's inner core pressure
- 2008
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 28:4, s. 437-441
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Tidskriftsartikel (refereegranskat)abstract
- The thermodynamic stability of S-substituting Si into a bcc Fe0.80Ni0.05SxSi(0.15-x) random alloy, with x=0.025 n (n=0-- 4), was investigated up to 350GPa by using an ab initio density functional method based on the full charge density-exact muffin-tin orbital-coherent potential approximation scheme. From the analysis of the calculated H values, we suggest that the FeNiSSi stoichiometry with zero sulphur content always behaves as the most stable system along the whole pressure range of 0-350GPa. As a general tendency, we found that the alloys with 6.8-8.1wt.% Si are energetically more stable than those with lower silicon content, thus supporting the dissolution mechanism for the Earth's inner core compositional model.
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| 5. |
- Olsen, J. Staun, et al.
(författare)
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High-pressure structural behavior of the double perovskite Sr2CrReO6 : an experimental and theoretical study
- 2009
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 29:1, s. 83-86
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Tidskriftsartikel (refereegranskat)abstract
- The high-pressure structural behavior of Sr2CrReO6 has been studied experimentally using synchrotron radiation and the diamond anvil cell and theoretically using density functional theory. The experimental zero-pressure bulk modulus is B0=1704GPa and the pressure derivative is B0'=4.71.0. These results compare well with the calculated values 172.6GPa and 5.7. A pseudo-cubic unit cell can describe the crystal structure at low pressure, but the tetragonal structure becomes evident at high pressure.
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| 6. |
- Talyzin, Alexandr, et al.
(författare)
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High pressure study of NaAlH4 by Raman spectroscopy up to 17 GPa
- 2006
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Ingår i: High Pressure Research. - : Informa UK Limited. - 0895-7959 .- 1477-2299. ; 26:3, s. 165-73
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Tidskriftsartikel (refereegranskat)abstract
- A high-pressure Raman study was carried out on NaA1H(4) up to 17 GPa using the diamond anvil cell method. In the pressure region 2-5 GPa, several of the original modes split. Although this might be a sign of some structural change, the spectral changes do not allow us to claim the existence of a clear phase transition in this pressure range. The spectra revert to their ambient pressure forms on decreasing pressure below < 3.0-1.4 GPa. A phase transition to beta-NaA1H(4) was found at 14-16 GPa. This phase transition is also reversible with an unusually strong hysteresis: the beta-NaA1H(4) can be followed upon decompression down to 3.9 GPa. Analysis of Raman data shows that this phase transition is compatible with a theoretical prediction of a strong volume collapse.
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| 7. |
- Tonpheng, Bounphanh, et al.
(författare)
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In situ high-pressure vulcanization and thermal properties of polyisoprene
- 2006
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Ingår i: High Pressure Research vol. 26. - : Taylor & Francis. ; , s. 415-419
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Konferensbidrag (refereegranskat)abstract
- Liquid cis-1,4-poly(isoprene) (PI) has been vulcanized under high pressures without using additives. Moreover, the thermal conductivity and heat capacity per unit volume of both unvulcanized (liquid state at room temperature) and vulcanized (rubbery state) PI have been measured, and found to be the same in both states. However, the relaxation behavior associated with the glass transition differs. The unvulcanized PI exhibits two clearly resolved relaxation processes near the glass transition whereas these tend to combine into one process in the vulcanized PI. Moreover, at the same pressure temperature co-ordinate, the relaxation time of the vulcanized sample (1 s at 220 K at atmospheric pressure) is longer than that of the unvulcanized sample.
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