Here is a list of some of the active research projects in the Korter group.

Structure and Dynamics of Hydrogen-Bonded Molecules and Clusters

Hydrogen bonding is ubiquitous in nature and governs a wide array of chemical and biological processes ranging from local structure in molecular liquids to the structure and folding dynamics of proteins. Although the hydrogen bond is well studied, its low-frequency vibrations - the large-amplitude motions involving stretching and bending along the actual hydrogen-bond coordinates - have been rarely investigated. Information about these vibrations offers exceptional insight into the potential energy surface of the interaction and so further enhances our understanding of the hydrogen bond and its impact on molecular structure and dynamics.

The low-frequency vibrations of hydrogen-bonded molecular clusters and biopolymers largely fall in the THz region (0.1-6 THz) of the electromagnetic spectrum. Our research program studies the structure and dynamics of hydrogen-bonded clusters and biopolymers in solution and the solid-state by utilizing THz time-domain spectroscopy (THz-TDS). One example of these studies is the clustering of phenol molecules in non-polar solvents (cyclohexane, carbon tetrachloride, etc.). Terahertz radiation allows us to directly observe the intermolecular vibrations of the phenol clusters. We have found that the THz spectra of these phenol solutions can only be explained by considering the samples as consisting of a complex equilibrium of phenol clusters ranging from dimers to tetramers.

Understanding the Chemical Origins of THz Spectra

One great challenge in THz spectroscopy of condensed-phase molecules is achieving a detailed understanding of the observed spectral features. The theoretical analysis of THz spectra is complicated by the nature of the vibrational motions that occur in this frequency range. The vibrational motions can be broadly described in terms such as intramolecular torsions, intermolecular stretching and bending, or lattice vibrations. All of these types of motions are heavily influenced by the molecular environment and therefore the challenge in predicting THz spectra from first principles lies in the accurate treatment of both the molecule of interest and its surroundings.

The Korter research group owns and maintains a 30-cpu cluster (AMD Opteron based) that is devoted to the analysis and prediction of THz spectra of molecular solids and solutions. A variety of software is used in these studies including CPMD, DMol3, GAMESS, and Gaussian. One particular project we have focused on is the analysis of the THz spectra of high explosives (RDX, TNT, etc.). The THz spectra of high explosives is of interest for security applications where the goal is to detect and identify harmful materials that may be contained within opaque containers. It is well established that many explosives exhibit characteristic THz spectra. However, the chemical origins of these spectra are not well known. To help answer these questions, we have utilized periodic boundary condition calculations to successfully model the THz spectrum of several solid-state explosives including HMX shown here.

Solid State Terahertz Spectroscopy of Biological Molecules   

For information about this project, contact Anna Fedor (amjose01@syr.edu)

The following agencies have generously provided us with financial and equipment support: