def FillAtomLookUp(atomData, indx):
    """create a dictionary of atom indexes with atom IDs as keys
    
    :param list atomData: Atom table to be used
    
    :returns: dict atomLookUp: dictionary of atom indexes with atom IDs as keys
    
    """
    atomLookUp = {}
    for iatm, atom in enumerate(atomData):
        atomLookUp[atom[indx]] = iatm
    return atomLookUp
