The files in this directory are a user-contributed package for LAMMPS.

The person who created these files is Andres Jaramillo-Botero at
CalTech (ajaramil@wag.caltech.edu).  Contact him directly if you have
questions.

--------------------------------------

Andres Jaramillo-Botero
California Institute of Technology (Caltech)
Chemistry and Chemical Engineering, 139-74
1200 E. California Blvd., Pasadena, CA 91125
Phone: (626) 395-3591
e-mail: ajaramil@wag.caltech.edu

Co-Authors: 
Julius Su (jsu@wag.caltech.edu)
William A. Goddard III (wag@wag.caltech.edu)

PACKAGE DESCRIPTION:

Contains a LAMMPS implementation of the electron Force Field (eFF)
currently under development at Caltech, as described in
A. Jaramillo-Botero, J. Su, Q. An, and W.A. Goddard III, JCC,
2010. The eFF potential was first introduced by Su and Goddard, in
2007.

eFF can be viewed as an approximation to QM wave packet dynamics and
Fermionic molecular dynamics, combining the ability of electronic
structure methods to describe atomic structure, bonding, and chemistry
in materials, and of plasma methods to describe nonequilibrium
dynamics of large systems with a large number of highly excited
electrons. We classify it as a mixed QM-classical approach rather than
a conventional force field method, which introduces QM-based terms (a
spin-dependent repulsion term to account for the Pauli exclusion
principle and the electron wavefunction kinetic energy associated with
the Heisenberg principle) that reduce, along with classical
electrostatic terms between nuclei and electrons, to the sum of a set
of effective pairwise potentials.  This makes eFF uniquely suited to
simulate materials over a wide range of temperatures and pressures
where electronically excited and ionized states of matter can occur
and coexist.

The necessary customizations to the LAMMPS core are in place to
enable the correct handling of explicit electron properties during
minimization and dynamics.

INSTALLATION:

via a normal LAMMPS package installation: make yes-user-eff

OTHERS FILES INCLUDED:

User examples are under examples/USER/eff
eFF tools are under tools/eff

ACKNOWLEDGMENTS:

Thanks to Steve Plimpton and Aidan Thompson for their input on the
LAMMPS architecture and for their help in customizing some of the
required LAMMPS core modules.

Version 01/2010: Special thanks to:
- Hai Xiao (Caltech) for reviewing the fixed-core implementation and 
  providing useful insights to improve it, and for his work on the effective core pseudopotential.
- Vaclav Cvicek (Caltech) for thoroughly revising the units, for finding a bug in the 
  fix_langevin_eff radial scaling factors, and for suggesting changes to clean-up the code.
- Patrick Theofanis (Caltech) for providing an optimized set of parameters for the Si ECP 
  (default) and for providing basic cases.
- Qi An (Caltech) for providing feedback on usage, application cases, and testing.

VERSION NOTES:
01/2010: Added support for fixed-core and effective core pseudopotentials [ECP]
(useful for C, Al, Si, O and other elements).  Cleaned up the code to make it
easier to maintain, revised support for real units, upgraded post-processing
and visualization tools, added support for "compute pair eff" to allow thermo
prints with the different eFF energy components (eke, epauli, ecoul and errestrain), 
fixed radial scaling factors in the eff langevin thermostat.


