Luczynska, Katarzyna published the artcileVibrational Response of Felodipine in the THz Domain: Optical and Neutron Spectroscopy Versus Plane-Wave DFT Modeling, Application In Synthesis of 72509-76-3, the main research area is felodipine plane wave DFT modeling optical neutron spectrum review.
We present a joint exptl. and computational terahertz (THz) spectroscopy study of the most stable polymorph (form I) of an antihypertensive pharmaceutical solid, felodipine (FLD). The vibrational response has been analyzed at room temperature by combining optical (THz-TDS, FT-IR, THz-Raman) and neutron (INS) terahertz spectroscopy. With the challenging example of a large and flexible mol. solid, we illustrate the complementarity of the exptl. techniques. We show how the results can be understood by employing ab initio modeling and discuss current progress in the field. To this end, we employ plane wave formulation of d. functional theory (plane wave DFT) along with harmonic lattice dynamics calculations (HLD) and ab initio mol. dynamics (AIMD) simulations. Based on a comprehensive theor. anal., we discover an inconsistency in the commonly accepted structural model, which can be linked to a distinct librational dynamics of the side ester chains. As a result, only a moderate agreement with the exptl. spectra can be achieved. We, therefore, propose an alternative structural model, effectively accounting for the influence of the large-amplitude librations and allowing for a comprehensive anal. of the vibrational resonances up to 4.5 THz. In that way, we illustrate the applicability of the computationally supported THz spectroscopy to detect subtle structural issues in mol. solids. While the provided structural model can be treated as a guess, the problem calls for further revision by means of high-resolution crystallog. The problem also draws a need of extending the THz experiments toward low-temperature conditions and single-crystal samples. On the other hand, the studied system emerges as a challenge for the DFT modeling, being extremely sensitive to the level of the theory used and the resulting description of the intermol. forces. FLD form I can be, hence, considered as a testbed for the use of more sophisticated theor. approaches, particularly relying on an advanced treatment of the van der Walls forces and going beyond zero-temperature conditions and harmonic approximation
Journal of Infrared, Millimeter, and Terahertz Waves published new progress about Crystal structure. 72509-76-3 belongs to class pyridine-derivatives, name is 3-Ethyl 5-methyl 4-(2,3-dichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate, and the molecular formula is C18H19Cl2NO4, Application In Synthesis of 72509-76-3.