Physical chemistry; laser spectroscopy; computational chemistry; crystallography; polymorphism

Measuring the low-frequency vibrations (generally sub-200 cm-1) of molecular crystals provides a remarkable mechanism for mapping the multi-dimensional intermolecular potential energy surface that governs their physical properties. The physical characteristics of molecular solids that are explored in the Korter research group range from the thermodynamic stability of crystalline polymorphs, to the hygroscopicity of drug formulations, to the mechanical elasticity of biopolymers.

Our primary tools for investigating such vibrations are terahertz (THz) time-domain spectroscopy (10 to 100 cm-1) and low-frequency Raman spectroscopy (5 to 300 cm-1), which together give us access to the complete set of lattice vibrations found in these samples. A large part of the work we do is the analysis and interpretation of the observed spectroscopic signatures, and this is accomplished through solid-state density functional theory and ab initio molecular dynamics simulations. We also make extensive use of single-crystal and powder X-ray diffraction techniques to support both the vibrational and computational parts of the research.

The ongoing research projects in the Korter group involve numerous fields and include national and international collaborations spanning academia, government, and industry. The following are a few representative research areas and select associated publications.

Polymorphism in Molecular Crystals

A. J. Zaczek, T. M. Korter, Polymorphism in cis-trans Muconic Acid Crystals and the Role of C-H···O Hydrogen Bonds. Crystal Growth & Design, 17: (8) 4458-4466 (2017).

S. P. Delaney, D. Pan, S. X. Yin, T. M. Smith, T. M. Korter, Evaluating the Roles of Conformational Strain and Cohesive Binding in Crystalline Polymorphs of Aripiprazole. Crystal Growth & Design, 13: (7) 2943-2952 (2013).

Structural and Energetic Details of Crystalline Solvates

T. M. Dierks, T. M. Korter, Comparison of Intermolecular Forces in Anhydrous Sorbitol and Solvent Cocrystals. Journal of Physical Chemistry A, 121: (30) 5720-5727 (2017).

M. T. Ruggiero, T. M. Korter, The Crucial Role of Water in Shaping Low-Barrier Hydrogen Bonds. Physical Chemistry Chemical Physics, 18: (7) 5521-5528 (2016).

Identification of Inorganic and Organic Pigments

A. D. Squires, R. A. Lewis, A. J. Zaczek, T. M. Korter, Distinguishing Quinacridone Pigments via Terahertz Spectroscopy: Absorption Experiments and Solid-State Density Functional Theory Simulations. Journal of Physical Chemistry A, 121: (18) 3423-3429 (2017).

M. T. Ruggiero, T. Bardon, M. Strliĉ, P. F. Taday, T. M. Korter, Assignment of the Terahertz Spectra of Crystalline Copper Sulfate and Its Hydrates via Solid-State Density Functional Theory. Journal of Physical Chemistry A, 118: (43) 10101-10108 (2014).

Detection and Characterization of Explosive Materials

T. R. Juliano, M. D. King, T. M. Korter, Evaluating London Dispersion Force Corrections in Crystalline Nitroguanidine by Terahertz Spectroscopy. IEEE Transactions on Terahertz Science and Technology, 3: (3) 281-287 (2013).

J. Wilkinson, C. T. Konek, J. S. Moran, E. M. Witko, T. M. Korter, Terahertz Absorption Spectrum of Triacetone Triperoxide (TATP). Chemical Physics Letters 478: (4-6) 172-174
(2009).