Lattice dynamics of polyacetylene as a one-dimensional system: Part I. The case of the trans perfect polymer

In this paper the lattice dynamics of trans-polyacetylene as a perfect one-dimensional crystal is treated. Dispersion curves, density of states and vibrational displacements are calculated. The results of the calculations are used to propose a vibrational assignment for (CH)_x, (CD)_x and (¹³CH)_x. Calculations have been made with a quadratic simplified valence force field (SVFF). The relationship between SVFF and the electron-phonon coupling model for polyacetylene, generally adopted in the literature, is discussed. Comparison with the calculations of other authors is made.