Research Interests
My research interests are multidisciplinary. They include
theoretical and computer simulations studies of the structure and
dynamics of liquids, ionic solutions, polar fluids, nanotubes,
and confined systems.
Collaborators and students are listed in parenthesis.
Theoretical and computational interests are focused on
- Nanocluster Growth and Coalescence Modulated by Ligands. (with M. Farshad, D.Suvlu )
- Thermodynamics of helix-coil transitions of polypeptides in carbon nanotubes.
(with S. Samaratunga, Dylan Suvlu, and Professor D. Thirumalai) - Proton transfer and the mobilities of the H+ and OH- ions from studies of
a dissociating model of water. (with Professor Song Hi Lee) - ab initio calculations of proton affinities (with Indira Silwal and Touradj Solouki)
- Water in Protein Cavities (with Hao Yin, and G. Hummer)
- Water in Confined Systems (with S. Vaitheeswarn, Hao Yin, and G. Hummer)
- Water conduction though carbon nanotubes (with G. Hummer, J.P. Noworyta and A. Waghe)
Previous research highlights are
- The hypernetted chain approximation (HNC) for electrolytes (with Professor Harold Friedman)
- Perturbation theories and Pade' approximants for the free energy of polar fluids (with Professor George Stell)
- The potential of mean force between ions in a polar solvent (with Dr. Ian McDonald)
- Dipolar ordering and electrostriction near a charged wall (with John Eggebrecht and Dr. Dennis Isbister)
- The sticky electrolyte model for weak electrolytes (with Song Hi Lee, Jianjun Zhu)
- Solvent dynamics on electron transfer reactions (with Jianjun Zhu)
- Computer Simulation studies of the structure and dynamics of Ions and Nonpolar solutes in bulk water
and in channels
(with S.Koneshan, Dr. J.P Noworyta and Professor Ruth Lynden -Bell) - Supercritical fluids (with J.P. Noworyta, S. Koneshan, R Lynden-Bell)
- Effect of chain formation on the phase transitions of polar fluids (with G. Dubey)
- Hydrophobic and hydrophilic effects by computer simulation of solvation entropy and free energy of simple solutes (with Professor Ruth Lynden-Bell)
- Elasticity of single molecules of double stranded DNA(with J. Lynch)
NSF Grant "Computer Simulations of Confined Systems"
Principal Investigator: Jayendran .C. Rasaiah
Water is ubiquitous and essential for life on earth (see for example the picture above) but it behaves very differently in confined systems in comparison to the bulk phase. Jay Rasaiah and his students (A.Waghe, S.Vaitheeswaran and H.Yin) and Dr. Gerhard Hummer, a collaborator at the National Institutes of Health, have explored the unusual behavior of water by computer simulation to produce striking new results concerning water in narrow pores and tiny nonpolar cavities. They essentially solve Newton’s laws of motion for these systems on a computer (molecular dynamics) to calculate the free energy of water occupancy and have also made movies of water entering and moving through narrow carbon nanotubes approximately 8 Angtroms wide. The water molecules form an essentially one-dimensional hydrogen-bonded chain in the narrow carbon nanotube through which it moves in bursts, triggered by density fluctuations at the tube ends that are open to a reservoir. Chemical modification or electric fields can empty the tubes and act as a water switch shown in the figure below.
The number N of water molecules inside the nanotube as a function of time for (a) unmodified (normal) and (b) modified (new) nanotube carbon-water interactions (c) structure of hydrogen bonded water chain inside nanotube.
Rasaiah and his collaborators at Maine and the NIH have also explored water filling of small nonpolar cavities of size ranging from 9-12 Angstroms in diameter. In this case the water forms hydrogen bonded clusters similar to some clusters already studied experimentally in the gas phase but now in a confined environment. This capture of water clusters in cavities provides a new way to isolate and investigate them, as they are of interest in cloud formation and chemical reactions in the upper atmosphere.
Water filling is very sensitive to cavity size and the strength of its interactions with the cavity walls. This observation has implications for water penetration into protein cavities, which Rasaiah and coworkers will study with support from a three year grant for $300,000 funded by the National Science Foundation. Dr. Rasaiah and his students Hao Yin and Aparna Waghe will also continue their studies, under this grant, of water filling carbon nanotubes, looking in particular at temperature effects on water occupancy to determine the factors (energy or entropy) that control filling. In addition, they will pursue previously initiated research on phase transitions of water between plates in the presence of electric fields, in an effort to better understand the behavior of water between charged membranes. The computer simulations will be carried on the Computing Cluster at The University of Maine Supercomputer Center.
Courses:
Graduate courses that I teach at various times are
- Statistical Thermodynamics (CHY 673)
- Principles of Quantum Chemistry (CHY 575)
- Phyiscal Chemistry 3 (CHY 475)
- Computer Simulation Methods (CHY 573)
- Physical Chemistry I (CHY 471)