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examples:potentials:pair:5

# Examples : Pair Potentials

Warning: This is an example potential. Please do NOT use it for any real simulations!

This is a simple pair potential that can be used in potfit. The analytic function used is a Lennard-Jones.

It makes use of the fixing parameters feature.

Example_Pair_5
#F 0 3
#T PAIR
#I 0 0 0
#E

type lj
cutoff 6.0
# The following parameter is fixed
epsilon 0.10    0.00    0.00
sigma   2.50    1.00    4.00

type lj
cutoff 6.0
# The following parameter is fixed
epsilon 0.10    0.10    0.10
sigma   2.50    1.00    4.00

type lj
cutoff 6.0
# The following parameter is fixed
epsilon 0.10    1.00    1.00
sigma   2.50    1.00    4.00

The optimization of single parameters can be disabled with this feature. The parameter will be removed from the optimization table and remain at its initial value. For all three lj-potentials in the above example the epsilon parameter will not be optimized, it will always have the fixed value of 0.1. To fix a parameter, the lower and upper bound have to be equal.

### makeapot

The example potential can be generated with the following makeapot command:

Hint: The parameters have to be fixed manually in the potential file!

makeapot -n 2 -i pair -f 3*lj