Structures, stabilities, and electronic properties of GaAs tubelike clusters and single-walled GaAs nanotubes

The geometric structures, stabilities, and electronic properties of (GaAs)_n tubelike clusters at up to n=120 and single-walled GaAs nanotubes (GaAsNTs) were studied by density functional theory (DFT) calculations. A family of stable tubelike structures with Ga-As alternating arrangement were observed when n≥8 and their structure units (four-membered rings and six-membered rings) obey the general developing formula. The average binding energies of the clusters show that the tubelike cluster with eight atoms in the cross section is the most stable cluster. The size-dependent properties of the frontier molecular orbital surfaces explain why the long and stable tubelike clusters can be obtained successfully. They also illustrate the reason why GaAsNTs can be synthesized experimentally. We also found that the single-walled GaAsNTs can be prepared by the proper assembly of tubelike clusters to form semiconductors with large bandgap.