Comparison Study of Atom-Centered and Plane-Wave Basis Sets in Solid-State DFT Calculations of Structure and Dynamics of Molecular Crystals
College of Arts and Sciences
Department of Chemistry & Biochemistry
Dr. Matthew D. King
Computational chemistry is widely used within multiple disciplines of chemistry and provides theoretical data that can assist in validating the evidence obtained from experimental data. A powerful computational method is that of solid-state density functional theory due to its proven accuracy and reproducibility in calculating crystalline structures and properties. There are important parameters to consider when performing solid-state DFT calculations, primarily in determining the proper basis set and density functional that is best suited for treatment of the system of interest. In this study, four molecular crystal systems, benzoic acid, naphthalene, glucose, and p-nitrophenol, were investigated using atom-centered basis sets and plane-wave basis sets using different functionals. The systems analyzed contain various intermolecular forces which will lead to results differentiated by each basis set and functional used. The atom-centered basis sets tested were 6-311G** and pob-TZVP, using functionals of varying theoretical complexity B3LYP, M06-L and PBE. The structure of each crystal system was optimized and the vibrational frequencies were calculated using the different combinations of basis sets and functionals. This is important because there are some combinations that will produce the most accurate structure, but may not accurately reproduce the full potential energy surface and associated vibrational frequencies. The frequencies of lattice vibrational modes were compared to experimental terahertz (THz) spectra of the crystals and RMSD values were determined. It was found that PBE/pob-TZVP produced the highest quality THz spectra in hydrogen-bonded crystals, and M06-L/pob-TZVP best reproduced the THz spectrum when π-bonding interactions were the primary stabilizing intermolecular forces.
Lopes, Bradley, "Comparison Study of Atom-Centered and Plane-Wave Basis Sets in Solid-State DFT Calculations of Structure and Dynamics of Molecular Crystals" (2019). 2019 Undergraduate Research and Scholarship Conference. 98.