.. _tutorial_basin_hopping:

======================
Basin Hopping Tutorial
======================

This tutorial explains how to run a basin hopping global optimization
calculation on a Lennard-Jones 13 particle.

.. image:: fig/lj13.png
    :align: center

Here is the con file of our starting structure:

.. literalinclude:: lj13.con

Here is the config.ini file::
    
    [Main]
    job=basin_hopping
    # specify the temperature used in the Monte-Carlo step acceptance
    temperature=500
    
    [Potential]
    # use the lennard-jones potential, in reduced-units
    potential=lj
    
    [Communicator]
    # run the client locally
    type=local
    # only run 1 client at a time
    number_of_cpus=1
    # run 10 jobs per invocation of eon
    num_jobs=10
    # search $PATH for a binary named eonclient
    client_path=eonclient
    
    [Basin Hopping]
    # perform 100 Monte-Carlo steps
    steps=100
    # use a gaussian distribution for the displacements instead of a uniform distribution
    displacement_distribution=gaussian
    # the standard deviation for the gaussian which is used to displace each degree of freedom
    displacement=0.3
    
    [Optimizer]
    # use the lbfgs optimizer
    opt_method=lbfgs
    # stop the optimization once the max force per atom drops below 0.001 eV/A
    converged_force=0.001
    # specifies the value of 1/H0 used in the lbfgs optimizer
    lbfgs_inverse_curvature=0.01
    
You should now have a directory with two files in it: ``config.ini`` and
``reactant.con``. To run the calculation run the ``eon`` script::

   $ eon 
   registering results
   0 (result) searches processed
   0 searches in the queue
   making 10 searches
   10 from random structures 0 from previous minima
   job finished in .//jobs/scratch/0
   job finished in .//jobs/scratch/1
   job finished in .//jobs/scratch/2
   job finished in .//jobs/scratch/3
   job finished in .//jobs/scratch/4
   job finished in .//jobs/scratch/5
   job finished in .//jobs/scratch/6
   job finished in .//jobs/scratch/7
   job finished in .//jobs/scratch/8
   job finished in .//jobs/scratch/9
   10 searches created

Eon first looks for any completed jobs. As this is the first time you have run
Eon, it finds no previous calculations to register. It then makes the input
files needed for the 10 basin hopping jobs and writes them to
``jobs/scratch/0..9``. Then eonclient is run in each of these directories.