CoNTub:  An Algorithm for Connecting Two Arbitrary Carbon Nanotubes

We have developed the first computer program for determining the coordinates of heterojunctions between two arbitrary carbon nanotubes. This software implements the topological algebra based on the concept of strip, a continuous subset of carbon rings containing all the topological defects (nonhexagonal carbon rings). The user easily generates any heterojunction by merely introducing the indices (i,j) and length of the two nanotubes to be connected. The resulting structure is immediately visualized and can be exported in the protein-data-bank (PDB) format. Two classes of heterojunctions are distinguished depending on whether a cone between the connected nanotubes is required. This method is applicable to all kinds of two nanotube heterojunctions, including Dunlap's knees and others related. In addition, this program also generates single- and multiwalled carbon nanotubes (SWNT and MWNT). This application has been implemented as a Java applet, and it is freely available at the following web address: http://www.ugr.es/local/gmdm/java/contub/contub.html