Boda Huang

Distribution patterns and controllable transport of water inside and outside charged single-walled carbon nanotubes

The density distribution patterns of water inside and outside neutral and charged single-walled carbon nanotubes (SWNTs) soaked in water have been studied using molecular dynamics simulations based on TIP3P potential and Lennard-Jones parameters of CHARMM force field, in conjunction with ab initio calculations to provide the electron density distributions of the systems. Water molecules show different electropism near positively and negatively charged SWNTs. Different density distribution patterns of water, depending on the diameter and chirality of the SWNTs, are observed inside and outside the tube wall. These special distribution patterns formed can be explained in terms of the van der Waals and electrostatic interactions between the water molecules and the carbon atoms on the hexagonal network of carbon nanotubes. The electric field produced by the highly charged SWNTs leads to high filling speed of water molecules, while it prevents them from flowing out of the nanotube. Water molecules enter the neutral SWNTs slowly and can flow out of the nanotube in a fluctuating manner. It indicates that by adjusting the electric charge on the SWNTs, one can control the adsorption and transport behavior of polar molecules in SWNTs to be used as stable storage medium with template effect or transport channels. The transport rate can be tailored by changing the charge on the SWNTs.

Density-functional theory calculations of XH3-decorated sic nanotubes (X ={C, Si}) : Structures, energetics, and electronic structures

We have investigated the structures, energetics, and electronic structures of XH3-radical-decorated silicon carbide nanotubes (SiCNTs), where X={C,Si}, using density-functional theory. Our results show that all the XH3 radicals can be chemically adsorbed on Si sites or C sites on the tube wall, with the adsorption energies ranging from −2.01 to −2.90eV for a (5,5) SiCNT. The modification in electronic structures of these decorated SiCNTs highly depends on the adsorption site rather than the XH3 species. The electronic structures of XH3-decorated SiCNTs demonstrate characteristics of n-type semiconductors for XH3 adsorbed on a C atom, whereas p-type semiconductors can be achieved by XH3 adsorption on a Si atom.

Theoretical prediction for the (AlN)12 fullerene-like cage-based nanomaterials

We have performed ab initio calculations on the stability and structural and electronic properties of the fullerene-like cage (AlN)n (n = 12) and the polymerized dimers and nanowires obtained from it. We found that the (AlN)12–(AlN)12 dimers and aluminum nitride (AlN)12-based nanowires polymerized from the (AlN)12 cage are more stable than (AlN)12. The optimized configurations of the nanowires are especially regular and exhibit an interesting dumbbell-shaped chain structure. We also calculated the electronic structures of all the constructed nanostructures. The two novel (AlN)12-based aluminum nitride nanowires have band gaps of 2.844 and 3.085 eV, respectively, implying that they are both wide-gap semiconductors and may be promising candidates for nanotechnology.

Electronic stopping powers of molybdenum metal for 19F ions at low velocity

Abstract Electronic stopping powers for 80–350 keV 19F ions in molybdenum were obtained by range measurement. Depth profiles of 19F in molybdenum were measured by using the 19F(p,αγ)16O resonant nuclear reaction at ER=872.1 keV. A proper convolution calculation method was used to extract the true distribution of fluorine from the experimental excitation yield curves. The electronic stopping powers were derived through fitting the projected range distributions, simulated by using the TRIM/XLL code, to the experimentally measured range distributions. The electronic stopping cross sections were compared with those obtained from Monte Carlo simulation codes.

An investigation of range distribution parameters for bismuth ion-implantation in silver gallium disulphur

Abstract Range distributions for bismuth ions implanted in AgGaS 2 in an energy range of 80–300 keV were investigated by using 2.1 MeV He 2+ Rutherford backscattering spectrometry (RBS). A convolution calculation method was used to extract the true distributions of bismuth from the measured RBS spectra. The range distribution parameters, R p and Δ R p , were obtained and compared with that obtained from Monte Carlo simulation. The experimental R p values agree with the Monte Carlo simulation values very well, but the experimental Δ R p values are systematically larger than those from the theoretical simulation.