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This package contains a fast implementation for LAMMPS of quantum-based
MGPT multi-ion potentials. The MGPT or model GPT method derives from
first-principles DFT-based generalized pseudopotential theory (GPT)
through a series of systematic approximations valid for mid-period
transition metals with nearly half-filled d bands. The MGPT method
was originally developed by John Moriarty at Lawrence Livermore
National Lab (LLNL).
In the general matrix representation of MGPT, which can also be applied
to f-band actinide metals, the multi-ion potentials are evaluated on the
fly during a simulation through d- or f-state matrix multiplication, and
the forces that move the ions are determined analytically. The mgpt
pair style in this package calculates forces and energies using an
optimized matrix-MGPT algorithm due to Tomas Oppelstrup at LLNL.
See the doc page for the pair_style mgpt command for full details on
using this package in LAMMPS. In particular, the user should note that
the MGPT potentials are explicitly volume dependent, requiring special
attention in their application. Useful example scripts are given in
the "examples/USER/mgpt" directory. These scripts show the necessary
steps to perform constant-volume calculations and simulations. It is
strongly recommended that the user work through and understand these
examples before proceeding to more complex simulations.
Specific MGPT potential data for the transition metals tantalum
(Ta4 and Ta6.8x potentials), molybdenum (Mo5.2 potentials), and
vanadium (V6.1 potentials) are contained in the LAMMPS "potentials"
directory. It is expected that MGPT potentials for additional
materials will be added over time.
The persons who created the USER-MGPT package are Tomas Oppelstrup
(oppelstrup2@llnl.gov) and John Moriarty (moriarty2@llnl.gov)
Contact them directly if you have any questions.
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