First-principles investigation in the Raman and infrared spectra of sp3 carbon allotropes

The Raman and infrared intensities of Bct-C4, C-carbon, F-carbon, M-carbon, O-carbon, P-carbon, T12, W-carbon, X-carbon and Z-carbon are calculated based on the density-functional theory and two discoveries are found. Firstly, their Raman peaks are distributed into two regions: from 600 to 1150 cm−1 and from 1150 to 1450 cm−1. As the Raman peaks of diamond and graphite are above 1300 cm−1, great attention should be paid between 600 and 1150 cm−1 in experiments. Secondly, differently from diamond, all of these newly proposed structures have infrared active modes. This suggests that infrared spectrum may give valuable information about the crystal structure of cold-compressed graphite.