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21.
Boron is available in the form of metal borates, especially of sodium and calcium, in nature[1]. The production of boron compounds has substantially increased recently due to increasing uses of these compounds in nuclear technology, in rocket engines as f… 相似文献
22.
The lattice dynamics of InAs under variable hydrostatic pressures is investigated on the basis of an ‘11-parameter’ rigid-ion model (RIM). The calculated phonon dispersion curves are in satisfactory agreement with the neutron scattering data (available for the TA modes only) measured at room temperature and atmospheric pressure. The one- and two-phonon densities of states functions and mode Gruneisen parameters have been computed at two arbitrary hydrostatic pressures. The effect of high pressure on the phonon dispersion curves is shown to lead to a typical ‘softening’ in the transverse acoustic modes and eventually to a phase trnasformation of the compound. 相似文献
23.
In this work, the thermal quantum correlations in two coupled double semiconductor charge qubits are investigated. This is carried out by deriving analytical expressions for both the thermal concurrence and the correlated coherence. The effects of the tunneling parameters, the Coulomb interaction, and the temperature on the thermal entanglement and on the correlated coherence are studied in detail. It is found that the Coulomb potential plays an important role in the thermal entanglement and in the correlated coherence of the system. The results also indicate that the Coulomb potential can be used for significant enhancement of the thermal entanglement and quantum coherence. One interesting aspect is that the correlated coherence capture all the thermal entanglement at low temperatures, that is, the local coherences are totally transferred to the thermal entanglement. Finally, the role played by thermal entanglement and the correlated coherence responsible for quantum correlations are focused on. It is shown that in all cases, the correlated coherence is more robust than the thermal entanglement so that quantum algorithms based only on correlated coherence may be more robust than those based on entanglement. 相似文献
24.
Moisés Cabo Eva Pellicer Emma Rossinyol Pau Solsona Onofre Castell Santiago Suriñach Maria Dolors Baró 《Journal of nanoparticle research》2011,13(9):3671-3681
The synthesis of NiCo2O4 spinel by several nanocasting strategies (i.e., multi-step nanocasting, one-step nanocasting and soft-templating), in which
nickel and cobalt nitrates are used as precursors and Pluronic P123 as surfactant, is explored. First, in the multi-step nanocasting,
the effect of the impregnation method (evaporation, solid–liquid and two-solvent) of the SBA-15 silica template on the morphology
of NiCo2O4 replica is investigated. The evaporation method seems to be the best choice to obtain mesoporous NiCo2O4 powder which, after calcination at 375 °C and subsequent template removal, displays the highest surface area (93.1 m2/g). We have also checked the feasibility of the one-step nanoscating approach for the synthesis of ordered NiCo2O4 arrays, though this methodology entails severe difficulties, mainly related to the different decomposition temperature of
the nitrate precursors and the P123 surfactant. Finally, randomly oriented, aggregated NiCo2O4 nanoparticles are obtained by means of P123 surfactant-assisted soft-templating approach. 相似文献
25.
It is quite relevant the extension of decoration transformation for quantum spin models since most of the real materials could be well described by Heisenberg type models. Here we propose an exact quantum decoration transformation and also showing interesting properties such as the persistence of symmetry and the symmetry breaking during this transformation. Although the proposed transformation, in principle, cannot be used to map exactly a quantum spin lattice model into another quantum spin lattice model, since the operators are non-commutative. However, it is possible the mapping in the “classical” limit, establishing an equivalence between both quantum spin lattice models. To study the validity of this approach for quantum spin lattice model, we use the Zassenhaus formula, and we verify how the correction could influence the decoration transformation. But this correction could be useless to improve the quantum decoration transformation because it involves the second-nearest-neighbor and further nearest neighbor couplings, which leads into a cumbersome task to establish the equivalence between both lattice models. This correction also gives us valuable information about its contribution, for most of the Heisenberg type models, this correction could be irrelevant at least up to the third order term of Zassenhaus formula. This transformation is applied to a finite size Heisenberg chain, comparing with the exact numerical results, our result is consistent for weak xy-anisotropy coupling. We also apply to bond-alternating Ising–Heisenberg chain model, obtaining an accurate result in the limit of the quasi-Ising chain. 相似文献
26.
From the density functional theory of Hohenberg-Kohn it is possible to prove that a molecular orbital is bonding (antibonding)
if its electronegativity is larger (smaller) than the electronegativities of the corresponding atomic orbitals. 相似文献
27.
The thermodynamics of the unitary (normalized spin) quantum and classical Ising models with skew magnetic field, for |J|β?0.9, is derived for the ferromagnetic and antiferromagnetic cases. The high-temperature expansion (β-expansion) of the Helmholtz free energy is calculated up to order β7 for the quantum version (spin S≥1/2) and up to order β19 for the classical version. In contrast to the S=1/2 case, the thermodynamics of the transverse Ising and that of the XY model for S>1/2 are not equivalent. Moreover, the critical line of the T=0 classical antiferromagnetic Ising model with skew magnetic field is absent from this classical model, at least in the temperature range of |J|β?0.9. 相似文献
28.
J. Carvalho N. Castro L. Chikovani T. Djobava J. Dodd S. McGrath A. Onofre J. Parsons F. Veloso The ATLAS Collaboration 《The European Physical Journal C - Particles and Fields》2007,52(4):999-1019
The ATLAS experiment sensitivity to top quark flavour changing neutral current (FCNC) decays was studied at LHC using tt̄
events. While one of the top quarks is expected to follow the dominant Standard Model decay t→bW, the other decays through
a FCNC channel, i.e. t→Zu(c), t→γu(c) or t→gu(c). Different types of analyses, applied to each FCNC decay mode, were compared.
The FCNC branching ratio sensitivity (assuming a 5σ signal significance) and 95% confidence level limits on the branching
ratios (in the hypothesis of signal absence) were obtained. 相似文献