Surface Induced Phenytoin Polymorph. 2. Structure Validation by Comparing Experimental and Density Functional Theory...

Area of Science:

• Crystallography
• Materials Science
• Spectroscopy

Background:

• Thin film structure determination is crucial for materials science.
• Previous methods combined X-ray diffraction (XRD) and crystal structure prediction, yielding a candidate structure for phenytoin form II.
• This candidate structure required further validation and refinement.

Purpose of the Study:

• To refine the crystal structure of phenytoin form II in thin films.
• To validate a previously proposed crystal structure using experimental data.
• To demonstrate the utility of low-wavenumber Raman spectroscopy in structure refinement.

Main Methods:

• Utilized grazing incidence X-ray diffraction (GIXRD) data analysis.
• Employed crystal structure prediction algorithms.
• Calculated and measured crystal Raman spectra in the low-wavenumber region.
• Compared experimental and calculated Raman spectra for validation.

Main Results:

• The initial candidate structure for phenytoin form II (Z=4, Z'=2) was identified as an energy saddle point.
• A lower symmetry minimum structure was identified through Raman spectral analysis.
• Excellent agreement was achieved between experimental and calculated Raman spectra for the refined structure.

Conclusions:

• Low-wavenumber Raman spectroscopy is effective for validating and refining crystal structures.
• The refined crystal structure of phenytoin form II (Z=4, Z'=2) provides a more accurate model.
• This combined XRD and Raman spectroscopy approach enhances thin film structure solution.