Title:   The Environment-Dependent Interatomic Potential:
         Theory and Application to Amorphous Silicon

Speaker: Dr. Martin Z. Bazant
         Dept. of Physics
         Harvard University

Date:    Friday, May 22, 4:00pm

Place:   M.I.T. Dept. of Nuclear Engineering, 
         Room 24-213 (Conference Room)
 
Abstract:

Silicon has become the testing ground for models of covalent bonding in
condensed matter. Since the 1980s, over 30 interatomic potentials for  
silicon have been proposed, with widely different functional forms and  
fitting strategies, but none appears to be capable of describing various  
important processes, such as dislocation motion or the liquid-to-amorphous
transition. In this work, analytic inversion techniques are developed to  
extract essential features of chemical bonding directly from experimental
data and ab initio calculations. These physical properties are
incorporated into a new functional form called the Environment-Dependent
Interatomic Potential (EDIP).  Fitting EDIP for silicon has led to a
superior overall description of defects and disordered phases.  For
example, amorphous silicon is reproduced remarkably well by EDIP, making
possible reliable atomistic studies of amorphous bulk defects, surfaces 
and phase transitions.