Dynamics of single selenium chains confined in one-dimensional nanochannels of AlPO4-5: Temperature dependencies of the first- and second-order Ramanspectra

The temperature dependence of the Raman spectrum of single helical Se chain s in nanochannels of AlPO4-5 was studied. Dramatic changes in the spectra d ue to structure transformations in this one-dimensional system are observed . The chains are found to be ordered at 77 K. Reversible weak disordering o f the chains (mainly due to the large-amplitude torsional vibrations) occur s with increasing temperature. At temperatures above similar to 340 K, a ph ase transition accompanied with a structural relaxation of the chains to th e strongly disordered state with unfixed dihedral angles ("torsional meltin g") is observed.