Home Page for the EnvironmentDependent Interatomic Potential
Introduction
The EnvironmentDependent Interatomic Potential (EDIP) is an efficient
and realistic model for interatomic forces in covalent solids and
liquids which incorporates recent theoretical advances in
understanding the environmentdependence of (sigma) chemical bonding
in condensed phases [1,2].
The parameterization for silicon [3] significantly outperforms
other existing potentials for silicon, including the popular
StillingerWeber and Tersoff potentials, when tested for bulk phases
(amorphous, liquid, crystal elasticity, thermal expansion,...), defects (point defects, stacking
faults,
dislocations,...) and phase transitions (crystal phases  amorphous  liquid).
EDIP has been used to study the liquidamorphous transition,
selfdiffusion, crystal platicity,
brittle fracture, solid
phase epitaxial growth, amorphous structures,
vibrational spectra, and much more. Recently, EDIP has also been
extended by N. A. Marks to
carbon by incorporating the effects of pibonding empirically
[Phys. Rev. B. (2001).
postscript].
Free software and Usage Agreement
Since it is a nontrivial task to efficiently and accurately compute
forces with a manybody potential like EDIP, tested and optimized
subroutines for force computation (written in C by Martin Bazant
and translated into fortran by Noam Bernstein in 1997, then
further optimized by Xianglong Yuan in 2002)
are provided below, which
may be incorporated into any molecular dynamics program.
Documentation within the source code explains the interface, which
takes as input the positions of the atoms and a Verlet neighbor list
for the interaction topology and returns as output the forces,
effective coordinations, energies and virial. By separating various
contributions to the virial, it is straighforward to compute the
stress tensor as well.
These subroutines are available at no cost to facilitate the
application and testing of EDIP. If the subroutines are used in
published research, however, it is with the understanding that the
theoretical work and empirical fitting which led to the potential will
be properly acknowledged. In particular, the following three
publications should be cited at once and in order:

M. Z. Bazant and E. Kaxiras,
Phys. Rev. Lett.
77, 4370 (1996).

M. Z. Bazant, E. Kaxiras, J. F. Justo,
Phys. Rev. B 56, 8542 (1997).

J. F. Justo, M. Z. Bazant, E. Kaxiras, V. V. Bulatov,
and S. Yip,
Phys. Rev. B 58, 2539 (1998).
More detailed descriptions of the
theory behind EDIP and the algorithm for force computation
can be found in:
M. Z. Bazant,
Interatomic Forces in
Covalent Solids, Ph.D. Thesis in Physics, Harvard University (1997).
(However, the thesis was written before the final parameter set was
obtained!)
Software Available to Download
 EDIP Subroutines:
These are the original subroutines which have been available since
1997 and tested extensively by many users.
In April 2002, Xiaolong Yuan somewhat
further optimize the force calculation,
yielding a typical performance boost of roughly 5% (before any compiler
optimization). The following two patched subroutines are recommended:
Other versions are also available along with
a detailed description of
the patches.
After you download the subroutines, please take a minute to send an email giving your name,
affiliation, address and a brief description of how you plan to use
EDIP. This information will be added to the database of researchers using EDIP
worldwide (which was automatically generated on the old server).
 Complete Parallel MD Package: Stefan Goedecker has incorporated EDIP into
a
freely available, userfriendly MD program written in fortran90. The subroutine
for EDIP
force calculation translated into fortran90 is also available separately.
 ConjugateGradient Energy Minimization Code: Joao Justo, one of
the original developers of EDIP, has
an optimized conjugategradient code using EDIP which is available upon request: jjusto@lme.usp.br.
Additional References
As the body of literature using EDIP grows, the following list
of subsequent pulications (not only by Bazant)
on applications and extensions of the potential
will eventually be maintained at this web site. Please come again.
If you would like to add papers and/or links to this list, please send an email.
EDIP for Silicon
 M. Z. Bazant, E. Kaxiras and J. F. Justo, The EnvironmentDependent
Interatomic Potential applied to silicon disordered structures and
phase transitions,
Mat. Res. Soc. Proc. 491, 339 (1997).
 M. de Koning, A. Antonelli, M. Z. Bazant, E. Kaxiras and J. F. Justo,
Finite temperature moleculardynamics study of unstable stacking
fault energies
in silicon, Phys. Rev. B 58 , 12555 (1998).
(eprint)
 N. Bernstein, M. J. Aziz, and E. Kaxiras, Atomistic simulations of
solidphase epitaxial growth in silicon, Phys. Rev. B 61, 6696
(2000).
 S. M. Nakhmanson and D. A. Drabold, Computer simulation of lowenergy
excitations in amorphous silicon with voids, J. Noncrystalline Solids
266269, 156 (2000).
 L. Brambilla, L. Colombo, V. Rosato, and F. Cleri,
Solidmelt interface velocity and diffusivity in lasermelt amorphous
silicon, Appl. Phys. Lett.
77, 2337 (2000).
 P. Keblinski, M. Z. Bazant, J. Dash, and M. Treacy,
Thermodynamic behavior of a model covalent material
described by the EnvironmentDependent Interatomic Potential,
Phys. Rev.
B 66, 4104 (2002). (eprint)
 M. MakiJaskari, K. Kaski, and A. Kuronen, Simulations of crack
initiation in silicon.
 M. Bazant and E. Kaxiras, On the structure of amorphous silicon and its
surfaces.
 J. Nord, K. Nordlund, and J. Keinonen, Amorphization mechanism and defect
stuctures in ion beam amorphized Si, Ge, and GaAs.
EDIP for Carbon
 N. A. Marks, Phys. Rev. B. 63, 0635401 (2001).
Inversion Methods
 M. Z. Bazant and E. Kaxiras, Modeling covalent bonding in solids by
inversion of cohesive energy curves, Phys. Rev. Lett.
77, 4370 (1996).
(
eprint)
 M. Z. Bazant and B. Trout, A
method to extract intermolecular potentials from the temperature
dependence of Langmuir curves, Physica A 300, 137173 (2001).
(eprint).
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