| 31. |
- Vitos, Levente, et al.
(författare)
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Elastic property maps of austenitic stainless steels
- 2002
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 88:15, s. 155501-
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Tidskriftsartikel (refereegranskat)abstract
- The most recent advances in theory and methodology are directed towards obtaining a quantitative description of the electronic structure and physical properties of alloy steels. Specifically, we employ ab initio alloy theories to map the elastic properties of austenitic stainless steels as a function of chemical composition. The so generated data can be used in the search for new steel grades, and, as an example, we predict two basic compositions with outstanding properties among the austenitic stainless steels.
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| 32. |
- Vitos, Levente, et al.
(författare)
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Modeling of alloy steels
- 2002
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Ingår i: Materials Today. - 1369-7021. ; 5:10, s. 14-23
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Forskningsöversikt (refereegranskat)abstract
- The use of computational quantum mechanics for the theoretical modeling of material properties of steel was described. Steel properties depend on the microstructure formed during the manufacturing process as well as on the concentartion and distribution of alloying elements and impurities. The computational methods allows reserachers to separate the effect of alloying elements on physical and chemical properties and to map the compositional distribution into the property distribution with arbitrary accuracy. The computational material design approach based on quantum theory with thermodynamics constitutes a profound advance in the design process of industrially relevant materials.
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| 33. |
- Wang, Y., et al.
(författare)
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Accurate quantum mechanical treatment of phonon instability : body-centred cubic zirconium
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:43, s. L695-L701
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Tidskriftsartikel (refereegranskat)abstract
- The T-1 N point and (omega point phonon anomalies for body-centred cubic (bcc) Zr are studied using an approach which goes beyond the traditional quasi-harmonic approximation and perturbation theory. We are able to reproduce, for the first time, the anomalous phonon behaviour in bcc Zr.
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| 34. |
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| 35. |
- Wang, Y., et al.
(författare)
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Melting of iron and other metals at earth's core conditions : A simplified computational approach
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:1
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Tidskriftsartikel (refereegranskat)abstract
- In order to Study melting of metals' at high pressure, we propose a different method which can be thought of as a generalization of the well-known Lindemann law. One essential interesting feature is that neither the Debye temperature nor the Gruneisen coefficient are used in the theory. We find that the method based on first-principles calculations can be used to model the pressure dependence of the melting properties of metals very well, predictions of the melting along the principal Hugoniot are calculated for Cu and Ta. In the case of Fe, the melting temperature is calculated at geophysically interesting pressures.
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| 36. |
- Wang, Y., et al.
(författare)
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Precise solution for H-point oscillation : Mo, Na, and Fe
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:25, s. L453-L459
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Tidskriftsartikel (refereegranskat)abstract
- In the existing theory of lattice dynamics, the central roles are played by the harmonic and the quasi-harmonic approximations. In this letter, we try to derive an accurate solution for the one-dimensional oscillator, exemplified by the H-point phonon in body-centred cubic metals. This problem is formulated such that it takes the form of a one-dimensional periodic system. Mo, Na, and Fe have been chosen as prototypes and we have examined the changes of the phonon energies with temperature and pressure. We are able to reproduce, for the first time, the anomalous temperature dependence of the H-point phonon energy for Mo.
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| 37. |
- Wang, Y., et al.
(författare)
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Reduction of shock-wave data with mean-field potential approach
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:11, s. 6616-6620
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Tidskriftsartikel (refereegranskat)abstract
- Based on ab initio calculated 0 K results for the assumed face- or body-centered-cubic ground state, the thermal volume expansion of the principal Hugoniot relative to the 300 K isotherm is calculated using the recently developed mean-field potential approach for Cu, Ta, Mo, Pt, and Au. Neglecting shock melting and phase dependence of the high-temperature equation of state, shock-reduced 300 K isotherms at pressures up to 1 TPa (10 Mbar) are derived for these metals by substracting the calculated thermal volume expansion from the experimental shock-wave data. This approach does not invoke any empirical assumptions regarding the Gruneisen parameters or heat capacities. The excellent agreement between such shock-reduced data and the normal standards or empirical reductions by other authors shows that the reduced results can be used as pressure standards for the widely employed static diamond-anvil-cell experiments.
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| 38. |
- Wang, Y., et al.
(författare)
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Thermodynamic properties at the Earth's core conditions and the shock-reduced isotherm of iron : a first-principles study
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:31, s. 7321-7335
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Tidskriftsartikel (refereegranskat)abstract
- First-principles thermodynamic calculations for metal iron (Fe) at ultrahigh pressures and temperatures are reported. The calculated results can be divided into three major parts: (i) the static 300 K equation of state and the dynamic shock-wave Hugoniot at pressures up to 1000 GPa; (ii) the shock-reduced data for the 300 K isotherm; and (iii) the thermodynamic properties under the Earth's core conditions. The calculations are parameter free in the sense that the cold part of the Helmholtz free energy is calculated using the full-potential linearized augmented-plane-wave method within the generalized gradient approximation. The thermal part due to the lattice ions is calculated using the recently developed classical mean-field potential approach, and the thermal part due to the thermal electrons is calculated using the one-dimensional numerical integration technique. The calculated results agree well with the available experimental data.
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| 39. |
- Wang, Y., et al.
(författare)
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Thermodynamic properties of MgO, Be, and W : a simplified computational approach
- 2002
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:44, s. 10895-10900
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Tidskriftsartikel (refereegranskat)abstract
- The recently developed classical mean-field potential (MFP) approach was employed to calculate the Helmholtz free energy for periclase (MgO), the Hugoniot equation of state for beryllium (Be) at pressures up to 2000 GPa, and the families of isentropic curves for tungsten (W). The excellent agreement between the theory and the experiment further demonstrated the high accuracy and applicability of the MFP approach.
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