Molecular dynamics simulation of [SnF.sup.2] nanostructures in the internal channels of single-walled carbon nanotubes

A molecular dynamics simulation of solid tin(II) fluoride nanostructures formed in internal channels of single-walled carbon nanotubes (SWCNTs) has been performed using two types of model potentialswithout and with inclusion of the polarization of ions. For the potential taking into account the polarization of ions, an ordered [SnF.sub.2]@SWCNT structure is reproduced: in SWCNT(10, 10), it has the form of the [SnF.sub.2] internal nanotube. At the same time, the [SnF.sub.2]@SWCNT(11, 11) structure is substantially disordered (glasslike). It has been found that heating of the [SnF.sub.2]@SWCNT model system produces a superionic state characterized by a high mobility of fluorine ions without migration of tin ions. The model potentials disregard the covalent character of Sn-F bonds and the specific interactions of a lone electron pair of the [Sn.sup.2+]ion. This makes it impossible to completely reproduce the properties of [SnF.sub.2] at normal pressures. However, some characteristics of the [SnF.sub.2] high-pressure modification can be reproduced if the polarization of ions is taken into account.