# Import the KohnSham module from ATK
from ATK.KohnSham import *
from os import path, rename

class MyVNLFile(VNLFile):
    def __init__(self, filename, backup=False):

        # Check if VNL file exists
        if ( path.isfile(filename) and backup ):
            rename(filename,filename+'.bak')

        VNLFile.__init__(self,filename)


# Set up elements and positions
elm = [ Hydrogen, Hydrogen ]
pos = [ ( +0.4, 0.0, 0.0)*Angstrom,
        ( -0.4, 0.0, 0.0)*Angstrom ]

# Add them to a configuration
h2 = MoleculeConfiguration(elm,pos)

# Open a VNL file and add the molecule to it
vnl_file = MyVNLFile('h2.vnl', True)
vnl_file.addToSample(h2, 'h2')