Study of the terahertz spectra of crystalline materials using NDDO
  semi-empirical methods: polyethylene, poly(vinylidene fluoride) form II and
  $\alpha$-D-glucose

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Abstract

Semi-empirical quantum chemistry methods offer a very interesting compromise between accuracy and computational load. In order to assess the performance of NDDO methods in the interpretation of terahertz spectra, the low frequency vibration modes of three crystalline materials, namely, polyethylene, poly(vinylidene fluoride) form II and $\alpha$-D-glucose have been studied using the PM6 and PM7 Hamiltonians and the results have been compared with the experimental data and former calculations. The results show good qualitative or semi-quantitative agreement with the experimentally observed terahertz spectra.