How to fit a potential using GULP and LAMMPS

How to use GULP

1. Download and make GULP (instructions are included in a README with GULP). Include any packages that you require for the specific potentials you are using.

2. GULP can be run by executing the gulp program and giving it an input file:

path/gulp-x.x/Src/gulp Gulp_Input

GULP comes with many different example input files, you will want to run GULP from the folder with the input file.

3. GULP structural data is given in the input file in the following format:

# Start of Structure
vectors
3.1023 0.0000 0.0000
1.4990 2.7214 0.0000
1.5040 0.8336 5.0333
fractional
Fe core 0.0000 0.0000 0.0000
Fe core 0.5000 0.5000 0.5000
O core 0.7500 0.7500 0.7500
O core 0.2500 0.2500 0.2500
space
P 1
observable
energy ev
-15.5000 100.0
end

Fractional can be changed for cartesian and both cores and shells can be defined. Atomic charges can be added to the end of each atom definition:

Fe core 0.0000 0.0000 0.0000 4.0

and many different observables can be defined, in this case the binding energy is given with a weighting.