Crystal
Structure and Vibrational Spectra of Poly(trimethylene
terephthalate) from Periodic Density Functional Theory Calculations
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Abstract
The crystal structure and the IR
spectrum of crystalline poly(trimethylene
terephthalate), PTT, have been investigated by means of periodic density
functional theory calculations including Grimme’s correction
for dispersion interactions. Both structural and spectroscopic results
have been critically compared to the experimental data taken from
the literature, showing very good agreement between theory and the
experiments. The previous spectral assignments, based only on experimental
investigations, have been revised, and further insights have been
obtained. Furthermore, spectroscopic markers of crystallinity or regularity
(i.e., of the regular conformation of the polymer chain) have been
proposed. In addition to the analysis of the IR spectra, the effect
of computational parameters on the crystal structure determination
(basis sets and parameters for Grimme’s correction) have been
analyzed. This work demonstrates that state-of-the-art computational
methods can provide an unambiguous description of the structural and
vibrational properties of crystalline polymers on the basis of the
peculiar intra- and intermolecular interactions occurring in different
macromolecular materials