Biography

John-Weeks


CONTACT INFORMATION

Office Phone: 301 405-4802
Office Address: 1108 IPST
 Email: jdw@umd.edu
 Group Website

Distinguished University Professor

Education

  • B.A.: Harvard University, Physics, Sept. 1961 – June 1965
  • Ph.D.: University of Chicago, Chemical Physics, Sept. 1965 – Sept. 1969
  • Post-Doctoral Research:
  • i.) University of California, San Diego-Chemical Physics, Sept. 1969 – Sept. 1971
  • ii) Cambridge University-Physics, Sept. 1971 – Sept. 1972

Professional Experience

  • 1995-present: Distinguished University Professor, University of Maryland
  • 1990-1995: Professor, Institute for Physical Science & Technology, and Department of Chemistry and Biochemistry, University of Maryland.
  • 1985-1990: Distinguished Member of Technical Staff, AT&T Bell Laboratories
  • 1972-1985: Member of Technical Staff, AT&T Bell Laboratories

Research Interests

Theoretical studies involving: nonuniform and confined fluids, ionic fluids, hydrophobic interactions, the static and dynamic properties of solid interfaces and thin films, density functional theory, pattern formation and crystal growth.

Maryland Biophysics Program

  • Major Recognitions and Honors
  • Fellow, American Association for the Advancement of Science, 2011
  • Member, National Academy of Sciences, USA 2009
  • Colloquium Ehrenfestii, University of Leiden 2001
  • Fellow, American Academy of Arts and Sciences, 2000
  • Joel Henry Hildebrand Award in the Theoretical and Experimental Chemistry of Liquids
  • (awarded by the American Chemical Society), 1990
  • Regent’s Lecturer, University of California, Berkeley, 1990
  • Fellow: American Physical Society, 1984

Significant Professional Service and Activities

1. Conferences and Society Organization:

  • Chair, Subdivision of Theoretical Chemistry, American Chemical Society, 1992-1993
  • Chair, Gordon Conference on Physics and Chemistry of Liquids, 1995; Vice-chair, 1993

2. Editorial Boards:

  • Chemical Physics; Advances in Chemical Physics; Journal of Chemical Physics 1994 -1997; Associate Editor,
  • Journal of Statistical Physics 2011- Editorial Board, Proceedings of the National Academy of Sciences, 2012-

Research

Theoretical research in the Weeks group has two main components. The first focuses on the properties of nonuniform and confined fluids, particularly those with long-ranged Coulomb or dipolar interactions. We have developed a new and general approach, called Local Molecular Field (LMF) theory, that determines both the structural and thermodynamic properties of such complicated nonuniform fluids by using a simpler  “mimic” system with only short ranged (essentially nearest neighbor) interactions but in an effective field that accounts for the averaged effects of the long-ranged interactions. Both qualitative reasoning and quantitative calculations are often much easier in the mimic system, and the effective field corrects major errors that can occur from simple truncations of Coulomb interactions alone.

GTwateraroundLJsolutecropThe figure above shows the water oxygen density around a hydrophobic solute with a diameter of 2 A for the full water model and for a truncated model with no long-ranged Coulomb or dispersion interactions. The very good agreement shows that the local hydrogen bond network is maintained around small hydrophobic solutes and that long ranged interactions play almost no role in this solute size regime.

In R. C. Remsing, J. M. Rodgers, and J. D. Weeks, “Deconstructing Classical Water Models at Interfaces and in Bulk,” J. Stat. Phys. 145, 313 (2011) we used ideas from LMF theory to divide the potential of the SPC/E water model into short and long ranged parts. The short ranged parts define a minimal reference network model that captures very well the structure of the local hydrogen bond network in bulk water while ignoring effects of the remaining long ranged interactions. This deconstruction can provide insight into the different roles that the local hydrogen bond network, dispersive van der Waals forces, and long ranged dipolar interactions play in determining a variety of properties of SPC/E and related classical models of water.

weeks impuritymodelThe figure shows a schematic top view of a vicinal surface in our model with steps represented by blue vertical segments that are placed on the links of a square lattice. The surface height decreases when crossing a step segment in the positive X direction

The second research area focuses on the static and dynamic properties of interfaces, concentrating in particular on the dynamics of steps on crystal surfaces. In M. Ranganathan and J.D. Weeks “Theory of Impurity Induced Step Pinning and Recovery in Crystal Growth from Solutions” Phys. Rev. Lett. 110, 055503 (2013) we extended the terrace-step-kink (TSK) model of crystal growth to impure solutions where the impurities act as barriers to step motion. Impurities are treated as in the classical Langmuir model and the coupling between impurities and steps produces new physics. The effects of supersaturation, step curvature, step repulsions, and impurities on step motion are treated in a unified free energy framework. The model reproduces several features seen in experiments on growth of potassium dihydrogen phosphate crystals, wherein a dead zone at low supersaturation and a recovery of crystal growth by motion of large coherent step bunches at larger supersaturation are observed.

Print Friendly