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.