Local-density-functional method is used to study the electronic properties of single-wall carbon nanotubes with very small diameters of about 4 Å, which have recently been synthesized inside zeolite channels. Our calculated results indicate that both the (5,0) and (3,3) tubes are metallic, while the (4,2) tube is semiconducting with a small indirect band gap. The metallicity of (5,0) is due to strong σ* and π* mixing induced by the large curvature of the tube. The calculated dielectric functions and breathing mode frequencies agree with experimentally measured absorption spectrum and Raman spectrum, respectively, giving strong support that these small radius tubes are indeed present inside the zeolite crystals.

We report a composite system for Li intercalation, in which ultrasmall-diameter (4 Å) carbon nanotubes are confined inside the channels of nanoporous zeolite crystals. The first-principles pseudopotential calculations show that there are several possible sites for lithium to be intercalated, including the interior and exterior of the nanotubes. The vapor phase adsorption and electrochemical measurements both indicate that the lithium capacity of the system can be; 10% by weight, which is higher than that of graphite intercalation compounds. The enhanced Li capacity makes the nanotubes-zeolite complex a plausible candidate for Li battery applications.

Adsorptions of both oxygen atoms and oxygen molecules on 4 Å single-wall carbon nanotubes, which have been fabricated using a templating method recently, are studied by the plane-wave pseudopotential method. Our calculations will provide some useful information on the stability of such ultrasmall tubes under ambient environment. We found that the calculated oxygen binding energy shows strong chirality dependence. Different adsorption pictures of singlet O2 can be used to select a single chirality from these ultrasmall-radius tubes.

Using density functional calculations and the nudged elastic band method, we investigate the adsorption pathways of singlet O2 on 4 Å single-wall carbon nanotubes, which have been recently fabricated using a templating method. We find that the reaction barriers for these ultrasmall-radius tubes are lower than those previously reported for larger-diameter tubes. Moreover, another chemisorbed product is identified for the (3,3) tube, and the reaction path is very different from those reported for larger armchair tubes.

First-principles pseudopotential method is used to study the stability of three kinds of 4 Å single-wall carbon nanotubes, which have been recently fabricated inside zeolite channels. The minimum energy path for unrolling the tube into a flat ribbon is calculated by the nudged elastic band technique. Our calculations suggest that all the three kinds of 4 Å tubes are stable when the zeolite framework is dissolved by acid, and the relative stability depends strongly on their chiralities. It is expected that the majority of the grown sample is (3,3) tube in free space.

Local-density-functional method is used to study the electronic properties of single-wall carbon nanotubeswith very small diameters of about 4 Å, which have recently been synthesized inside zeolite channels. Ourcalculated results indicate that both the (5,0) and (3,3) tubes are metallic, while the (4,2) tube is semiconductingwith a small indirect band gap. The metallicity of (5,0) is due to strong s* and p* mixing induced by thelarge curvature of the tube. The calculated dielectric functions and breathing mode frequencies agree withexperimentally measured absorption spectrum and Raman spectrum, respectively, giving strong support thatthese small radius tubes are indeed present inside the zeolite crystals.

We report a composite system for Li intercalation, in which ultrasmall-diameter ~4 Å! carbonnanotubes are confined inside the channels of nanoporous zeolite crystals. The first-principlespseudopotential calculations show that there are several possible sites for lithium to be intercalated,including the interior and exterior of the nanotubes. The vapor phase adsorption and electrochemicalmeasurements both indicate that the lithium capacity of the system can be; 10% by weight, whichis higher than that of graphite intercalation compounds. The enhanced Li capacity makes thenanotubes-zeolite complex a plausible candidate for Li battery applications.

Adsorptions of both oxygen atoms and oxygen molecules on 4 Å single-wall carbon nanotubes, which havebeen fabricated using a templating method recently, are studied by the plane-wave pseudopotential method.Our calculations will provide some useful information on the stability of such ultrasmall tubes under ambientenvironment. We found that the calculated oxygen binding energy shows strong chirality dependence. Differentadsorption pictures of singlet O2 can be used to select a single chirality from these ultrasmall-radius tubes.

First-principles pseudopotential method is used to study the stability of three kinds of 4 Åsingle-wall carbon nanotubes, which have been recently fabricated inside zeolite channels. Theminimum energy path for unrolling the tube into a flat ribbon is calculated by the nudged elasticband technique. Our calculations suggest that all the three kinds of 4 Å tubes are stable when thezeolite framework is dissolved by acid, and the relative stability depends strongly on theirchiralities. It is expected that the majority of the grown sample is (3,3) tube in free space.