Theory, Simulation, and Modeling
Description
Theoretical chemistry at Penn is particularly strong in the areas of statistical mechanics, quantum dynamics, and molecular dynamics, with emphasis on the theory and computer simulation of biophysical systems, novel materials and condensed phase processes. Research efforts involve the development and application of new computational methods, often with applications to the design of new molecular systems. Theoretical chemists in the department focus on such problems as designing proteins with defined structure and function, performing molecular simulations of molecules within biological membranes at the atomic level, and developing quantum mechanical methods to tailor the surface properties of inorganic materials. Excellent computing facilities are available within the department.
This picture (red = Pb, blue = Zr, green = Ti, black = O) illustrates why
Pb(Zr{1-x},Tix)O3 (called "PZT") is the key smart material in medical ultrasound
devices, naval SONAR detection and broadcast, and ferroelectric RAM memory.
All the cations want to move off-center in their oxygen cages. The color
maps in each cage indicate how strongly the drive to increase chemical
bonding is for each ion. In general, the cation displacements align (vectors
mostly to the left and up) due to long-range dipole-dipole coupling. Locally,
the Pb atoms try to avoid larger Zr atoms and move toward smaller Ti atoms,
explaining the angle scatter in the displacement pattern. This scatter
weakens the energy of alignment, making this material more responsive to
external electric fields. Rappe Group
