92 lines
4.1 KiB
Plaintext
92 lines
4.1 KiB
Plaintext
This package contains a LAMMPS implementation of the electron Force
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Field (eFF) currently under development at Caltech, as described in
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A. Jaramillo-Botero, J. Su, Q. An, and W.A. Goddard III, JCC,
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2010. The eFF potential was first introduced by Su and Goddard, in
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2007.
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eFF can be viewed as an approximation to QM wave packet dynamics and
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Fermionic molecular dynamics, combining the ability of electronic
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structure methods to describe atomic structure, bonding, and chemistry
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in materials, and of plasma methods to describe nonequilibrium
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dynamics of large systems with a large number of highly excited
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electrons. We classify it as a mixed QM-classical approach rather than
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a conventional force field method, which introduces QM-based terms (a
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spin-dependent repulsion term to account for the Pauli exclusion
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principle and the electron wavefunction kinetic energy associated with
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the Heisenberg principle) that reduce, along with classical
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electrostatic terms between nuclei and electrons, to the sum of a set
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of effective pairwise potentials. This makes eFF uniquely suited to
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simulate materials over a wide range of temperatures and pressures
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where electronically excited and ionized states of matter can occur
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and coexist.
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The necessary customizations to the LAMMPS core are in place to
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enable the correct handling of explicit electron properties during
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minimization and dynamics.
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See the doc page for the pair_style eff/cut command to get started.
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There are example scripts for using this package in
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examples/PACKAGES/eff.
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There are auxiliary tools for using this package in tools/eff.
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The person who created this package is Andres Jaramillo-Botero at
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CalTech (ajaramil at wag.caltech.edu). Contact him directly if you
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have questions.
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-------------------------
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AUTHOR INFORMATION:
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Andres Jaramillo-Botero
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California Institute of Technology (Caltech)
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Chemistry and Chemical Engineering, 139-74
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1200 E. California Blvd., Pasadena, CA 91125
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Phone: (626) 395-3591
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e-mail: ajaramil@wag.caltech.edu
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Co-Authors:
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Julius Su (jsu@wag.caltech.edu)
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William A. Goddard III (wag@wag.caltech.edu)
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ACKNOWLEDGMENTS:
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Thanks to Steve Plimpton and Aidan Thompson for their input on the
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LAMMPS architecture and for their help in customizing some of the
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required LAMMPS core modules.
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Version 01/2010: Special thanks to:
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- Hai Xiao (Caltech) for reviewing the fixed-core implementation and
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providing useful insights to improve it, and for his work on the effective core pseudopotential.
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- Vaclav Cvicek (Caltech) for thoroughly revising the units, for finding a bug in the
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fix_langevin_eff radial scaling factors, and for suggesting changes to clean-up the code.
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- Patrick Theofanis (Caltech) for providing an optimized set of parameters for the Si ECP
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(default) and for providing basic cases.
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- Qi An (Caltech) for providing feedback on usage, application cases, and testing.
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VERSION NOTES:
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01/2010: Added support for fixed-core and effective core
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pseudopotentials [ECP] (useful for C, Al, Si, O and other elements).
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Cleaned up the code to make it easier to maintain, revised support for
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real units, upgraded post-processing and visualization tools, added
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support for "compute pair eff" to allow thermo prints with the
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different eFF energy components (eke, epauli, ecoul and errestrain),
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fixed radial scaling factors in the eff langevin thermostat.
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12/2011: Added support for "zero" option in fix langevin/eff (see doc), and
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adjusted fix_langevin_eff.cpp to correctly thermostat between nuclear and electronic dof
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(required additional scaling of friction term in the Langevin equations of motion).
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Radial electron mass now scales as a function of system dimension.
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Bug fixes:
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(10-2011): Thanks to Christian Chenard-Lemire (U Montreal) for reporting a bug in the
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fixed pair_eff_cut.cpp fixedcore-pseudocore interactions (an incorrect index and a missing
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elec-core call to account for the 2 electrons from the fixed core.)
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(12-2011): Corrected undefined natom variable in fix_langevin_eff (recent changes in
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main fix_langevin class caused compilation error in user-eff).
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Corrected thermostat in fix langevin/eff as described in version 12/2011.
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