Dynamical modes of a graphite surface, on top and in the middle- by unfolding the observed temperature dependent displacement-displacement auto-correlation function

Making use of the unfolding technique to determine the phonon frequency distribution function (FDF) from the temperature dependent displacement-displacement auto-correlation function suggested by the authors, the experimentally observed displacement-displacement auto-correlation functions of a graphite surface located either at the top or in the middle of the crystal have been unfolded. The final unfolded FDF shows marked differences for the two cases, exhibiting the potentiality of the unfolding technique to accurately determine the dynamics and hence the difference in the FDF of the two layers, located at different sites in a crystal.