  By means of non-resonant Raman spectroscopy and density functional theory
calculations, we measure and assign the vibrational spectrum of two distinct
two-dimensional lead-iodide perovskite derivatives. These two samples are
selected in order to probe the effects of the organic cation on lattice
dynamics. One templating cation is composed of a phenyl-substituted ammonium
derivative, while the other contains a linear alkyl group. We find that modes
that directly involve the organic cation are more prevalent in the
phenyl-substituted derivative. Comparison of the temperature dependence of the
Raman spectra reveals differences in the nature of dynamic disorder, with a
strong dependence on the molecular nature of the organic moiety.
