Ab initio studies on the geometrical and vibrational structures of polymers

Abstract

The geometrical structures and vibrational spectra of all‐trans, cis‐transoid and trans‐cisoid polyacetylene, and all‐trans‐polymethineimine have been calculated using the energy gradient scheme for one‐dimensional polymers based on the ab initio crystal orbital method. The vibrational spectra of all‐trans‐polyacetylene reported here are in good agreement with the experimental results. We have proposed a reassignment of the Raman spectra of cis‐transoid‐ polyacetylene. The vibrational spectra of the trans‐cisoid polyacetylene are calculated theoretically. The bond alternant structure of all‐trans‐polymethineimine is more stable than the equidistant one, and the vibrational spectra are calculated for this structure.