Study of optical vibrations modes of mineral graphite by micro raman spectroscopy

We present experimental and theoretical Raman spectra of natural graphite mineral of Sonora, Mexico. In this work, we take the advantage of the utility of the RAMAN spectroscopy as a technique to determine the crystallinity and structure of graphite mineral. The RAMAN spectroscopy provides information that can be used to determine the degree of graphitization, which in turn can be used to know the metamorphic degree of the host rock. The resulting RAMAN spectra of graphite were divided in first and second order regions, in the first region (1100-1800cm^-1) the E_2g vibration mode with D_6h crystal symmetry occurs at 1580cm^-1 (G band) that indicates poorly organized graphite, additional bands appears in the first order region at 1350 cm^-1 (D band) called the defect band, and another at 1620 cm ^-1 (D*band). The second-order region (2200-3400cm^-1) shows several bands at ∼2400 ∼2700 ∼2900 ∼3300cm^-1, all of them attributed to electron-phonon interactions or combination scattering. The density functional theory calculations were applied to determine the vibrational properties and the stacking layers of graphite.