| 1. |
- Borg, Mikael, et al.
(författare)
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Density of configurational states from first-principles calculations: The phase diagram of Al-Na surface alloys
- 2005
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Ingår i: ChemPhysChem. - : Wiley. - 1439-7641 .- 1439-4235. ; 6:9, s. 1923-1928
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Tidskriftsartikel (refereegranskat)abstract
- The structural phases of AlxNa1-x surface alloys have been investigated theoretically and experimentally. We describe the system using a lattice gas Hamiltonian, determined from density functional theory together with Monte Carlo (MC) calculations. The obtained phase diagram reproduces the experiment on a quantitative level. From calculation of the (configurational) density of states by recently introduced Wang-Landau MC algorithm, we derive thermodynamic quantities such as free energy and entropy which are not directly accessible from conventional MC simulations. We accurately reproduce the stoichiometry, as well as the temperature at which an order-disorder phase transition occurs, and demonstrate the crucial role, and magnitude of the configurational entropy.
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| 2. |
- Pentcheva, R., et al.
(författare)
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A combined DFT/LEED-approach for complex oxide surface structure determination : Fe3O4(001)
- 2008
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Ingår i: Surface Science. - : Elsevier BV. - 0039-6028 .- 1879-2758. ; 602:7, s. 1299-1305
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Tidskriftsartikel (refereegranskat)abstract
- A combination of density functional theory (DFT) calculations and low energy electron diffraction (LEED) analysis is used to determine the surface structure of Fe3O4 0 00). We find that the surface is rich in oxygen and the observed (root 2- x root 2-)R45 degrees reconstruction is a result of a Jahn-Teller distortion as established by recent DFT-calculations [R. Pentcheva, F. Wendler, H.L. Meyerheim, W. Moritz, N. Jedrecy, M. Scheffler, Phys. Rev. Lett. 94 (2005) 126101]. The corresponding Pendry reliability factor is 0.34. Furthermore, we investigate the influence of the preparation conditions (temperature, oxygen pressure) on the LEED intensities of natural and synthetic samples. The electron scattering phase shifts used in the analysis of the LEED spectra are derived from two methods, one based on the DFT electron densities and another employing an overlap of atomic potentials with optimized muffin-tin radii. Both approaches lead to similar results.
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| 3. |
- Thelander, Claes, et al.
(författare)
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Nanowire-based one-dimensional electronics
- 2006
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Ingår i: Materials Today. - 1369-7021. ; 9:10, s. 28-35
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Tidskriftsartikel (refereegranskat)abstract
- During the last half century, a dramatic downscaling of electronics has taken place, a miniaturization that the industry expects to continue for at least a decade. We present efforts to use the self-assembly of one-dimensional semiconductor nanowires(1) in order to bring new, high-performance nanowire devices as an add-on to mainstream Si technology. The nanowire approach offers a coaxial gate-dielectric-channel geometry that is ideal for further downscaling and electrostatic control, as well as heterostructure-based devices on Si wafers.
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