Static vs dynamic DFT prediction of IR spectra of flexible molecules in the condensed phase: The (ClCFCF(CF)OCFCH) liquid as a test case.

First-principles molecular dynamics (FPMD) simulations in the framework of Density Functional Theory (DFT) are carried out for the prediction of the infrared spectrum of the fluorinated molecule ClCFCF(CF)OCFCH in liquid and gas phase. This molecule is characterized by a flexible structure, allowing the co-existence of several stable conformers, that differ by values of the torsional angles. FPMD computed spectra are compared to the experimental ones, and to Boltzmann weighted IR spectra based on gas phase calculations.