1,721,130 research outputs found
Structural, electronic and ferroelectric properties of croconic acid crystal: A DFT study
No full textThe recent discovery of high polarization at room temperature in croconic acid crystals as large as 21 mu C cm(-2) [Horiuchi et al., Nature, 2010, 463, 789] has lead to renewed interest in organic ferroelectrics, a promising class of materials for future electronic devices. We present here an extended ab initio study of this molecular crystal, using different approximations for the exchange-correlation functionals, ranging from local and semi-local types to more sophisticated hybrid functionals and van der Waals corrected functionals. Furthermore, by using distortion mode analysis, we focus on the different contributions to the polarization and on their microscopic origins
Beyond standard local density approximation in the study of magnetoelectric effects in Fe/BaTiO3 and Co/BaTiO3 interfaces
No full textFirst-principles density functional theory (DFT) simulations for Fe/BaTiO3 and Co/BaTiO3 junctions have been performed with different treatments of the exchange–correlation potential, ranging from standard semilocal density approximations to a Hubbard-like approach and to hybrid functionals. With the aim of elucidating the role of correlations in the microscopic interplay between ferroelectricity and magnetism in the interfacial region, we find that, compared to standard DFT approximations, Hubbard-like approaches and hybrid functionals do not qualitatively modify the physical origin behind magnetoelectric effects driven by interfacial orbital hybridization. Rather, more accurate treatments of correlations for both Fe/BaTiO3 and Co/BaTiO3 interfaces predict a stronger change of the interface magnetization upon switching the direction of polarization in the ferroelectric layer
Electric fields and valence-band offsets at strained [111] heterojunctions
No full textAb initio full-potential linearized augmented plane wave (FLAPW) [H. J. F. Jansen and A. J. Freeman, Phys. Rev. B 30, 561 (1984); M. Weinert, H. Krakauer, E. Wimmer, and A. J. Freeman, ibid. 24, 864 (1981)] calculations have been performed for the [111] ordered common atom strained layer superlattices (in particular, the common-anion GaSb/InSb system and the common-cation InAs/InSb system). We have focused our attention on the potential line up at the two sides of the homopolar isovalent heterojunctions considered, and, in particular, on its dependence on the strain conditions and on the strain induced electric fields. We propose a procedure to locate the interface plane, where the band alignment could be evaluated; furthermore, we suggest that the polarization charges, due to piezoelectric effects, are approximately confined to a narrow region close to the interface and do not affect the potential discontinuity. We find that the interface contribution to the valence band offset is substantially unaffected by strain conditions, whereas the total band line up is highly tunable as a function of the strain conditions. Finally, we compare our results with those obtained for the [001] heterojunctions
The Co2MnGe Heusler compound: A first principles study of the bulk phase and of the interface with GaAs
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EFFECTS OF EPITAXIAL STRAIN AND ORDERING DIRECTION ON THE ELECTRONIC-PROPERTIES OF GASB/INSB AND INAS/INSB SUPERLATTICES
No full textA trade-investment model for distribution of wealth
No full textEconophysics provides a strategy for understanding the potential mechanisms underlying the anomalous distribution of wealth found in real societies. We present a computational nonlinear stochastic model for the distribution of wealth that depends upon three parameters and two mechanisms: trade and investment. To avoid economic paradoxes, the trade mechanism is assumed to be related to the poorer trader???s wealth and to statistically advantage the poorer of the two traders. The two mechanisms together are shown to generate a distribution that reproduces the full range of the empirical wealth distribution, and not only the inverse power-law tail that Pareto found in western societies at the end of the 19th century
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