Velizhanin KA, Kilina S, Sewell TD, Piryatinski A. First-principles-based calculations of vibrational normal modes in polyatomic materials with translational symmetry: application to PETN molecular crystal. J Phys Chem B. 2008 Oct 23;112(42):13252–7. doi: 10.1021/jp804980a. PMID: 18821785.
First-Principles-Based Calculations of Vibrational Normal Modes in Polyatomic Materials with Translational Symmetry: Application to PETN Molecular Crystal