A crystallographic analysis of the atom positions in the unit cell of the R-phase of the TiNi shape memory alloy has been performed. In addition to a homogeneous shape change the atoms are found to shuffle in the [111](B2) and [-211](B2) directions during the B2 to R-phase transformation. The origin of these shuffles is found to be a complex interaction between [110][1-10] transverse acoustic and [111] longitudinal acoustic soft phonon modes.