Raman Spectroscopy of Nanopolycrystalline Diamond Produced from Shungite at 15 GPa and 1600°C

Raman investigations and ab initio calculations of natural diamond-lonsdaleite originating from New Caledonia

“…3b). The slightly larger FWHM and low-frequency shift of the band may be induced by lower crystallinity (nano-sized) of the natural cubic diamond [48,51,52] as well as the heat of the sample (this effect was described in Supplementary materials of [53]), the last was control in our experiment with low power of exiting laser beam. Additionally, the contribution of lonsdaleite in Raman spectrum of lonsdaleite-diamond mixture (natural or synthetic samples) can lead to shift of total wide Raman band from 1332 cm − 1 to lower value (up to 1320 cm − 1 [38,47,49]).…”

“…Considering various structures of sp 3 -carbon atoms, a series of superhard carbon allotropes is predicted, described, and investigated [40][41][42][43][44][45][46][47][48][49][50]. Two of them are observed in nature, 3C-diamond and 2H-diamond [8].…”