~~NOTOC~~
====== Examples : Pair Potentials ======

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//**Warning:**//
This is an example potential. Please do NOT use it for any real simulations!
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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 **invariant potentials** feature.

<code potfit Example_Pair_6>
#F 0 3
#T PAIR
#I 1 0 0
#E

# This potential is invariant, it will not be optimized
type lj
cutoff 6.0
epsilon 0.10    0.00    1.00
sigma   2.50    1.00    4.00

type lj
cutoff 6.0
epsilon 0.10    0.00    1.00
sigma   2.50    1.00    4.00

type lj
cutoff 6.0
epsilon 0.10    0.00    1.00
sigma   2.50    1.00    4.00
</code>

The invariant potentials feature is the equivalent of the fixing a parameter, except it applies
to an entire potential. In the example the first lj-potential will not be optimized. This
is indicated in the ''#I'' header line. Each item therein corresponds to a potential. Setting
the value to 1 disables the optimization.

==== makeapot ====

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

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Invariant potentials have to be set up manually in the potential file!
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  makeapot -n 2 -i pair -f 3*lj