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D. G. Pettifor 《辐射效应与固体损伤》2013,168(3-4):121-126
The different roles played by the valence s and d electrons in determining the bulk properties of pure transition metals is described. In the light of this the expected behaviour of the inert gas-metal and metal-metal interatomic potentials is discussed. 相似文献
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An accurate density-functional method is used to study systematically half-metallic ferromagnetism and stability of zincblende phases of 3d-transition-metal chalcogenides. The zincblende CrTe, CrSe, and VTe phases are found to be excellent half-metallic ferromagnets with large half-metallic gaps (up to 0.88 eV). They are mechanically stable and approximately 0.31-0.53 eV per formula unit higher in total energy than the corresponding nickel-arsenide ground-state phases, and therefore would be grown epitaxially in the form of films and layers thick enough for spintronic applications. 相似文献
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Gimenez-Lopez Mdel C Räisänen MT Chamberlain TW Weber U Lebedeva M Rance GA Briggs GA Pettifor D Burlakov V Buck M Khlobystov AN 《Langmuir : the ACS journal of surfaces and colloids》2011,27(17):10977-10985
Anisotropy of intermolecular and molecule-substrate interactions holds the key to controlling the arrangement of fullerenes into 2D self-assembled monolayers (SAMs). The chemical reactivity of fullerenes allows functionalization of the carbon cages with sulfur-containing groups, thiols and thioethers, which facilitates the reliable adsorption of these molecules on gold substrates. A series of structurally related molecules, eight of which are new fullerene compounds, allows systematic investigation of the structural and functional parameters defining the geometry of fullerene SAMs. Scanning tunnelling microscopy (STM) measurements reveal that the chemical nature of the anchoring group appears to be crucial for the long-range order in fullerenes: the assembly of thiol-functionalized fullerenes is governed by strong molecule-surface interactions, which prohibit formation of ordered molecular arrays, while thioether-functionalized fullerenes, which have a weaker interaction with the surface than the thiols, form a variety of ordered 2D molecular arrays owing to noncovalent intermolecular interactions. A linear row of fullerene molecules is a recurring structural feature of the ordered SAMs, but the relative alignment and the spacing between the fullerene rows is strongly dependent on the size and shape of the spacer group linking the fullerene cage and the anchoring group. Careful control of the chemical functionality on the carbon cages enables positioning of fullerenes into at least four different packing arrangements, none of which have been observed before. Our new strategy for the controlled arrangement of fullerenes on surfaces at the molecular level will advance the development of practical applications for these nanomaterials. 相似文献
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D.G. Pettifor 《Solid State Communications》1978,28(8):621-623
The accuracy of a recently proposed simple analytic theory of the heats of formation ΔH of transition metal alloys is demonstrated by comparison with the tight binding coherent potential approximation calculations of Van der Rest et al. The d charge transfer is evaluated within a model that includes explicitly the deformation of the pure metal bands on alloying. 相似文献
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CM Thaker S Rayaprol Krushna Mavani DS Rana MS Sahasrabudhe SI Patil DG Kuberkar 《Pramana》2002,58(5-6):1035-1039
The effect of simultaneous substitution of a fluctuating cation and a divalent cation in LaMnO3 perovskite modifies the properties of the material to exhibit large valence colossal magnetoresistance (CMR) effect. A good
example of these properties is (La1−2x
Pr
x
Ca
x
)MnO3 (LPCMO) type CMR material. In this communication it is reported that, with the increase in x (for x=0.1, 0.15, 0.2), the T
c varies between 100 and 120 K with improvisation in metal-insulator transition. Interestingly, resistance increases with x from few hundred ohms to few kilo ohms with corresponding decrease in the unit cell volume. The results of the studies using
X-ray diffraction (XRD), electrical resistivity, magnetoresistance and ac susceptibility measurements on LPCMO samples for
understanding the structural, transport and magnetic properties are discussed in detail. 相似文献
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§ 1.Introduction WearegivenkindependentWishartdensitiesofthe (p +q)× (p +q)randomsymmetricpositivedefinitematricesG1,… ,Gktobeg(Gi) =Kexp -12 trR- 1i Gi Gi12 (ni- q-p- 1) ,(1 )wherei=1 ,… ,k,andRidenotesthepopulationcorrelationmatrixofthei thpopulationandKasagenericletterdenote… 相似文献
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Bozec D Howson MA Hickey BJ Shatz S Wiser N Tsymbal EY Pettifor DG 《Physical review letters》2000,85(6):1314-1317
We have carried out an experimental and theoretical study of the magnetoresistance MR(H) in the CPP (current perpendicular to the planes) mode for two types of magnetic multilayers that differ only in the ordering of the magnetic layers: [Co(10 A)/Cu(200 A)/Co(60 A)/Cu(200 A)](N) and [Co(10 A)/Cu(200 A)](N)[Co(60 A)/Cu(200 A)](N). The series resistor model predicts that in the CPP mode MR(H) is independent of the ordering of the layers. Nevertheless, the measured MR(H) curves were found to be completely different for the two cases. Calculations based on a realistic band structure and the Kubo formula show that the results are a consequence of a long mean free path. 相似文献