1. Analysis of infrared and Raman spectra calculated by molecular dynamics
- Author
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D Fischer, Daniel Bougeard, E Henssge, and D Dumont
- Subjects
Infrared ,Chemistry ,Organic Chemistry ,Analytical chemistry ,Infrared spectroscopy ,Dichroism ,Potential energy ,Molecular physics ,Spectral line ,Analytical Chemistry ,Inorganic Chemistry ,symbols.namesake ,Dipole ,Molecular dynamics ,symbols ,Raman spectroscopy ,Spectroscopy - Abstract
Molecular dynamics (MD) is a common and powerful method to simulate chemical systems at the atomic level. The calculation of vibrational spectra is a less common application of MD simulations. In this work, the interest was focused on the analysis of vibrational spectra (infrared and Raman) of polymers from MD data. For this purpose two methods were developed: the simulation of polarized IR spectra (IR dichroism) and the spectra of particular internal coordinates. Molecular dynamic calculations reproduce the polarized infrared spectra with a high accuracy in comparison with experimental data. It is shown that these data can be obtained from an analysis of the three-dimensional orientation of the molecular dipole moment. The calculated spectrum of any particular coordinate yields a direct correlation between a vibrational band and the concerned coordinate. We find an excellent agreement between these calculated spectra for polyethylene and the potential energy distribution (PED) derived from NCA. These spectra allow a quick assignment of vibrational bands also for IR or Raman inactive modes, which are found in power spectrum. Thus, MD is shown to be a method complementary to NCA.
- Published
- 1999
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