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2007
A tight-binding based bond-order potential BOP has been constructed for the fcc transition metal iridium that includes explicitly only d orbitals in the evaluation of the total energy.We show that hybridization between the nearly free electron sp band and the unsaturated covalently bonded d orbitals is important in determining the relative stabilit…
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2007
Iron-chromium alloys are characterized by a complex phase diagram, by the small negative enthalpy of mixing at low Cr concentrations in the bcc -phase of Fe, and by the inversion of the short-range order parameter. We present Monte Carlo simulations of the binary Fe-Cr alloy based on the cluster expansion approximation for the enthalpy of the syste…
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2007
Direct numerical simulations DNS provide a means to test phenomenological models for the scaling properties of intermittent MHD turbulence. The well-known model of She and Leveque, when generalized to MHD, is in good agreement with the DNS in three dimensions, however, it does not coincide with DNS in two dimensions 2D. This is resolved here using …
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2007
We present a bond-order potential BOP for the bcc transition metal tungsten. The bond-order potentials are a real-space semiempirical scheme for the description of interatomic interactions based on the tight-binding approximation. In the hierarchy of atomic-scale-modeling methods the BOPs thus provide a direct bridge between electronic-structure an…
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2007
The destabilization of ideal magnetohydrodynamic ballooning modes at finite rotation shear is demonstrated for the model s - equilibrium by exploiting low magnetic shear, s , to simplify the two-dimensional stability problem to a one-dimensional eigenvalue problem. This simpler calculation captures the same features as exhibited by a full two-dimen…
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2007
We present the results of a numerical investigation of the interaction between the ITER ICRF antenna plug (external matching option) and the surrounding wall blanket modules with the commercial software CST Microwave Studio (MWS). In particular we study the RF currents circulating on and between these modules with a simplified rectangular model of …
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2007
The structural changes during the phase change between the amorphous and crystalline phase in Ge 2 Sb 2 Te 5 have been the subject of intense study due to the importance of Ge 2 Sb 2 Te 5 in phase change memory devices. In our study, the energetics of the transition between the crystalline and the amorphous phase of Ge 2 Sb 2 Te 5 is explored using…
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2007
Recent advances in modeling the effects of anisotropic energetic ion distributions have enabled the development of a complete coherent physics explanation of sawtooth stabilization in both conventional and spherical tokamaks. As an example, a complete model has been developed to explain the asymmetric stabilization of sawteeth with respect to neutr…
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2007
We investigate the structure and mobility of single self-interstitial atom and vacancy defects in bodycentered- cubic transition metals forming groups 5B vanadium, niobium, and tantalum and 6B chromium, molybdenum, and tungsten of the Periodic Table. Density-functional calculations show that in all these metals the axially symmetric 111 self-inters…
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2007
The linear stability of dissipative drift electrostatic modes in tokamak plasmas is studied numerically with an extended version of the gyrokinetic code [Kinezero C. Bourdelle and et al. , Nucl. Fusion 42 , 892 (2002)] including a modified Krook collision operator to account for collisional effects on the trapped electron response. This new version…
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