# Ken Jordan

The Jordan group's research interests lie in several areas:

**Accomodation of excess charge by water clusters:** Excess electrons and protons in water are engaged in a wide range of important chemical, biological, and geochemical processes. Our group has been especially interested in understanding how these charged particles are accommodated by the water networks. Much of our work in this area is in collaboration with the Johnson group at Yale, which uses vibrational predissociation spectroscopy as a probe of the structure of the clusters. The resulting spectra tend to be highly anharmonic, providing a significant challenge to theory. Our group has been engaged in the development of model Hamiltonian approaches to characterize excess electrons in water and to understand the trends in the OH stretch spectra of protonated water clusters.

**Long-range correlation effects:** We are engaged in developing methods to describe long-range correlation effects in molecules, clusters, and at surfaces. This work includes extensions of the dispersion-correlated atomic potential (DCACP) procedure of Rothlesberger and co-workers, and the use of quantum Drude oscillators to describe long-range correlation effects between excess electrons and molecules and clusters.

**Quantum Monte Carlo methods:** The DMC method is highly parallel and can be run over tens of thousands of CPU cores enabling calculation of accurate energies for systems for which large basis set CCSD(T) calculations are not feasible. The main approximation of DMC calculations is the fixed-node approximation, which is made to maintain fermionic character of the wavefunction. Our research is focused on the development of improved nodal approximations via the use of multiconfigurational trial functions.

**Sustainability**: We are using computational methods to address a range of problems relevant to clean energy and sustainability. These include modeling heat transport in methane hydrate and other hydrates and elucidation of the role of water in the uptake of CO2 by clays. In these studies, we are using classical Monte Carlo and molecular dynamics simulation methods with classical force fields.

- "Comparison of Density Functional and MP2 Calculations on the Water Monomer and Dimer," K. Kim,
__K. D. Jordan__, J. Phys. Chem. 98, 10089 (1994) - "Spectral Signatures of Hydrated Proton Vibrations in Water Clusters," Jeffrey M. Headrick, Eric G. Diken, Richard S. Walters, Nathan I. Hammer, Richard A. Christie, Jun Cui, Evgeniy M. Myshakin, Michael A. Duncan, Mark A. Johnson,
__Kenneth D. Jordan__, Science 108, 1765 (2005) - "Infrared Signature of Structures Associated with the H+(H2O)n (n = 6 to 27) Clusters," J.-W. Shin, N. I. Hammer, E. G. Diken, M. A. Johnson, R. S. Walters, T. D. Jaeger, M. A. Duncan, R. A. Christie,
__K. D. Jordan__, Science 304, 1137 (2004) - "Studies of the temporary anion states of unsaturated hydrocarbons by electron transmission spectroscopy,"
__Kenneth D. Jordan__, Paul D. Burrow, Acc. Chem. Res. 11, 341 (1978) - "Infrared Spectrum of a Molecular Ice Cube: The S4 and D2d Water Octamers in Benzene-(Water)8," Christopher J. Gruenloh, Joel R. Carney, Caleb A. Arrington, Timothy S. Zwier, Sharon Y. Fredericks,
__Kenneth D. Jordan__, Science 13, 5319 (1997)

- "Preface: Special Topic: From Quantum Mechanics to Force Fields", Jean-Philip Piquemal, and Kenneth D. Jordan, The Journal of Chemical Physics 147, 161401 (2017)
- "H
_{4}: A model system for assessing the performance of diffusion Monte Carlo calculations using a single Slater determinant trial function," Kevin Gasperich, Michael Deible, and__Kenneth D. Jordan__, The Journal of Chemical Physics 147, 074106 (2017) - "Implementation of analytical gradients and of a mixed real and momentum space DVR method for excess electron systems described by a self-consistent polarization model," Tae Hoon Choi, Tijo Vazhappilly, and
__Kenneth D. Jordan__, Journal of Chemical Physics 147, 161717 (2017) - "Comment on a spurious prediction of a non-planar geometry for benzene at the MP2 level of theory," Nagaprasad Reddy Samala,
__Kenneth D. Jordan__, Chem. Phys. Lett., 669, 230-232 (2017) - "Stabilization calculations of the low-lying temporary anions states of Be, Mg, and Ca," Michael F.Falcetta, Nathan D.Reilly,
__Kenneth D.Jordan__, Chemical Physics 482, 23 (2017)