faculty

Professor Emeritus of Chemistry
Ph.D., Harvard University

Theoretical Studies of Molecular Structure and Reactivity

Phone: (734) 764-3148
E-mail: llohr@umich.edu

One very important and increasingly appreciated area is that of studying relativistic effects on the chemistry of heavy elements. We have developed a relativistically parameterized semiempirical molecular orbital method called "REX" which has been applied systematically to a wide variety of compounds including those of gold, mercury, thalium, lead, bismuth, polonium, and the actinides. More recently we have extended the procedure to the description of the band structure of periodic solids formed from heavy elements.

We are also actively engaged in extensive computational studies of the electronic and geometrical structures, as well as the reactivity, of such species as the gas-phase radicals NO₃ and PO₃. More generally we are interested in establishing the interdependence of electronic properties with acid/base properties. An especially rewarding area of application of ab initio methods has proven to be in the study of centrifugal distortions of rotating gas-phase molecules. Through the definition of a centrifugal distortion pathway we have been able to facilitate the interpretation of the high resolution molecular spectra of such species as SF₆ and have characterized the energies and shapes of rotating clusters of rare-gas atoms.

REPRESENTATIVE PUBLICATIONS

1. LL Lohr, RR Sharp, and SM Abernathy. "Paramagnetically Induced NMR Relaxation in Solutions Containing S - 1 Ions: A New Theoretical Model" J. Chem. Phys. 1997, 107, 7620-7629.
2. LL Lohr and D Sundholm. "An ab initio Characterization of Diphosphorus Trisulfide, P₂S₃" J. Mol. Struct. 1997, 413, 495-500.
3. LL Lohr. "Rotational Dependence of Turning Point Surfaces and Vibrational Frequencies for Lennard-Jones Argon Clusters" Mol. Phys. 1997,91,1097-1105.
4. SM Abernathy, JC Miller, LL Lohr, and RR Sharp. "Nuclear Magnetic Resonance-paramagnetic Relaxation Enhancements: Influence of Spatial Quantization of the Electron Spin when the Zero-field Splitting Energy is Larger than the Zeeman Energy" J. Chem. Phys. 1998,108,8012-8019.
5. LL Lohr. "Quantum Chemical Studies of Carbon-13 Equilibrium Fractionation in Ion-molecule Reactions" J. Chem. Phys. 1998, 109, 4035-4046.