Adamantane is the simplest structure of diamondoid (hydrocarbon molecules) with molecular formula C10H16 [1]. Adamantane crystallizes in a face centered cubic (FCC) lattice and is very stable. Vibrational modes of adamantane analyzed using theoretical prediction of vibrational frequencies. Density functional theory (DFT) was selected to compute theoretically the vibrational frequencies of adamantane via Gaussian 03 software [2] with regard to structural optimization after drawn by Gauss View. Via harmonic approximation, the vibrational frequencies calculated by diagonalization of the mass-weighted Hessian (second derivatives of the energy with regard to the nuclear displacements
