Atomistic simulations of inorganic nanowires.
ABSTRACT Inorganic nanowires, such as those of metals, semiconductors and oxides, have attracted much research interest due to their unique material properties and present many possibilities for the development of revolutionary applications in materials science and technology. There are abundant reports on experimental works covering various aspects of nanowires including fabrication, structural analysis and property characterization. Theoretical studies have also been carried out to provide researchers with a better understanding of nanowire structural characteristics and the mechanisms that affect their properties. This report gives a brief introduction to the numerical methodologies commonly used for the analysis of nanowires followed by a review of theoretical works focusing on the unique structures of nanowires, their stability and related mechanical properties. The current state of research and development of nanowires is presented together with some comments on the future direction of theoretical studies on inorganic nanowires.
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ABSTRACT: The effects of charge transfer between atoms on an amorphous SiO2 surface were studied by comparing a model with fixed charge (FQ) and a model that takes into consideration charge transfer by the charge equilibration (QEq) method. The QEq surface has more oxygen atoms and denser structures compared to the FQ sample. We found, on the surface of the QEq sample, three-coordinated Si with an O-Si-O bond angle in the range of 109-115°. This structure is similar to that of the experimentally observed E' center (≡Si.). We also found a structure similar to the nonbridging oxygen hole center (≡Si-O.), which has been observed experimentally on a silica glass surface. These structures were not observed in the FQ model. The results suggest that consideration of the charge transfer is essential to reproduce the defect structure of the silica glass surface.Journal of Applied Physics 01/2002; 92:4408-4413. · 2.19 Impact Factor
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ABSTRACT: The evolution of the structure and conductance of an Al nanowire subject to a tensile stress has been studied by first-principles total-energy simulations. Our calculations show the correlation between discontinuous changes in the force (associated to changes in the bonding structure of the nanowire) and abrupt modifications of the conductance as the nanowire develops a thinner neck, in agreement with the experiments. We reproduce the characteristic increase of the conductance in the last plateau, reaching a value close to the conductance quantum $G_0 = 2 e^2 / h$ before the breaking of the nanowire. A dimer defines the contact geometry at these last stages, with three channels (one dominant) contributing to the conductance. Comment: 4 pages, 4 figuresPhysical Review B 11/2002; · 3.66 Impact Factor
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ABSTRACT: Many nanostructures experience structural transformation, either from one type of crystalline structure to another or from one orientation to another orientation within the same crystalline structure. Using a combination of ab initio calculations and analytical formulation, we show that such structural transformation is a direct result of surface reconstruction. In particular, our ab initio results show that infinite large ZnO nanoplates and infinite long ZnO nanowires transform from wurtzite to graphitic structure below a critical thickness or diameter. Our analytical formulation further shows that nanowires of finite length can go through the same structural transformation at larger critical diameters.Applied Physics Letters 01/2007; · 3.52 Impact Factor