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.

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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

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.