Modelling the structure of GaAs and InAs nanowires

Using ab initio methods, we study the stability of thin (diameters up to 10 nm) GaAs and InAs nanowires. Modelled nanowires were constructed using bulk atomic positions along six different crystallographic directions of either zinc-blende or wurtzite structures. Taking into account the reconstruction of the nanowire surfaces, we have found that, for diameters of up to 50 Å, the most stable nanowires adopt the wurtzite (0001) structure—for such diameters the free energy of zinc-blende nanowires along any crystallographic axis is always larger than that of the wurtzite (0001) ones. To calculate the free energy in nanowires with larger diameters, we have approximated their total energy by the sum of congruous bulk and bulk surface energies. In these nanowires the interplay between the wurtzite and zinc-blende structures was demonstrated. The band structure and the density of charge in the nanowires have also been calculated.