Identification and Quantification of Polymorphism in the Pharmaceutical Compound Diclofenac Acid by Terahertz Spectroscopy and Solid-State Density Functional Theory

摘要

ABSTRACT: Polymorph detection and quantification in crys-ntalline materials is a principle interest of the pharmaceuticalnindustry. Terahertz (THz) spectroscopy can be used for suchnanalytical applications since this technique is sensitive to thenintermolecular interactions of molecules in the solid state.nUnderstanding the fundamental nature of the lattice vibrationalnmotions leading to absorptions in THz spectra is challenging,nbut may be achieved through computational approaches. In thisnstudy, the THz spectra of two diclofenac acid polymorphs werenobtained by THz spectroscopy, and the vibrational characters of the observed absorptions were analyzed using solid-state densitynfunctional theory (DFT). The results demonstrate the quantitative capacity of THz spectroscopy and the reliability and utility ofnsolid-state DFT in the calculation of low-frequency vibrational motions.