LCAO calculations of SrTiO₃ nanotubes

The large-scale first-principles simulation of the structure and stability of SrTiO₃ nanotubes is performed for the first time using the periodic PBE0 LCAO method. The initial structures of the nanotubes have been obtained by the rolling up of the stoichiometric SrTiO₃ slabs consisting of two or four alternating (001) SrO and TiO₂ atomic planes. Nanotubes (NTs) with chiralities (n,0) and (n,n) have been studied. Two different NTs were constructed for each chirality: (I) with SrO outer shell, and (II) with TiO₂ outer shell. Positions of all atoms have been optimized to obtain the most stable NT structure . In the majority of considered cases the inner or outer TiO₂ shells of NT undergo a considerable reconstruction due to shrinkage or stretching of interatomic distances in the initial cubic perovskite structure. There were found two types of surface reconstruction: (1) breaking of Ti-O bonds with creating of Ti = O titanyl groups in outer surface; (2) inner surface folding due to Ti–O–Ti bending. Based on strain energy calculations the largest stability was found for (n,0) NTs with TiO₂ outer shell.