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- Belonoshko, Anatoly B., et al.
(författare)
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Molybdenum at High Pressure and Temperature : Melting from Another Solid Phase
- 2008
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Ingår i: Physical review letters / publ. by the American Physical Society. ; 100:13, s. 135701-
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Tidskriftsartikel (refereegranskat)abstract
- The Gibbs free energies of bcc and fcc Mo are calculated from first principles in the quasiharmonic approximation in the pressure range from 350 to 850 GPa at room temperatures up to 7500 K. It is found that Mo, stable in the bcc phase at low temperatures, has lower free energy in the fcc structure than in the bcc phase at elevated temperatures. Our density-functional-theory-based molecular dynamics simulations demonstrate that fcc melts at higher than bcc temperatures above 1.5 Mbar. Our calculated melting temperatures and bcc-fcc boundary are consistent with the Mo Hugoniot sound speed measurements. We find that melting occurs at temperatures significantly above the bcc-fcc boundary. This suggests an explanation of the recent diamond anvil cell experiments, which find a phase boundary in the vicinity of our extrapolated bcc-fcc boundary.
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- Kochetov, A. E., et al.
(författare)
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Interaction of Au nanowires with impurities
- 2008
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Ingår i: European Physical Journal B. - : Springer Science and Business Media LLC. - 1434-6028 .- 1434-6036. ; 61:4, s. 441-444
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Tidskriftsartikel (refereegranskat)abstract
- We report the results of our first-principles studies of the interaction between an infinite monoatomic gold nanowire and a carbon-monoxide molecule. We show that the gold monoatomic nanowire is capable of absorbing the CO molecule at the distances of about 1.8 angstrom and forms a bond with the carbon atom. Further, we find that dissociation of the CO molecule as the source of gold nanowire contamination with carbon, which is widely discussed in literature as the possible reason for the striking stability of gold nanowires under stretching, is thermodynamically unfavored.
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| 8. |
- Mikhaylushkin, Arkady, 1977-
(författare)
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Structural properties of Fe1-xNix compressed and heated to the Earth's core conditions
- 2008
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Ingår i: FPLO Workshop,2008. - Dresden : Germany.
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Konferensbidrag (refereegranskat)abstract
- Cosmochemical, geochemical, and geophysical studies provide evidences that Earth's core contains iron with substantial (5 to 15 at. %) amounts of nickel and/or impurities of light elements. The results of our combined first-principles study and in-situ and temperature-quenched laser-heated diamond anvil-cell experiments on the high-pressure high-temperature structural behavior of pure Fe and Fe_0.9 Ni_0.1 alloy are reported. Our temperature-quenched experiments indicate that the face-centered cubic (fcc) phase of pure iron can exist in the pressure-temperature region above 160 GPa and 3700 K. In accord our theoretical results show that the fcc phase of Fe becomes as stable as the hexagonal-close-packed (hcp) phase at Earth's core condition (P ~ 300-360 GPa and T around 5000-6000 K). Further we demonstrate by means of in-situ angle-dispersive x-ray diffraction in internally heated diamond anvil cells (DACs) that by substantial alloying of Fe with Ni (10 at. %) a body-centered cubic phase can stabilize in the Earth's core. Our results give an evidence that the actual structure of the the Earth's core could be a complex phase, which is very sensitive to the presence of impurities of nickel, sulfur, silicon, etc.
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