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# Atomization energy

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# Atomization energy

The following script will calculate the atomization energy of a nitrogen molecule.

    from ase import Atoms
    from ase.calculators.emt import EMT

First, an `Atoms` object containing one nitrogen is created and a fast EMT calculator is attached to it simply as an argument.

    atom = Atoms('N')
    atom.calc = EMT()

The total energy for the isolated atom is then calculated and stored in the `e_atom` variable.

    e_atom = atom.get_potential_energy()

The `molecule` object is defined, holding the nitrogen molecule at the experimental bond length `d=1.1` Angstrom.

    d = 1.1
    molecule = Atoms('2N', [(0.0, 0.0, 0.0), (0.0, 0.0, d)])

    import matplotlib.pyplot as plt

    from ase.visualize.plot import plot_atoms

    fig, ax = plt.subplots()
    plot_atoms(molecule, ax, rotation=('90x,0y,90z'))
    ax.set_axis_off()

The EMT calculator is then attached to the molecule and the total energy is extracted into the `e_molecule` variable.

    molecule.calc = EMT()
    e_molecule = molecule.get_potential_energy()

The atomization energy is the energy required to break the bond, meaning that it is the negative energetic difference between the molecule and twice the single atom’s energy.

    e_atomization = -1.0 * (e_molecule - 2 * e_atom)

Finally we print the relevant energies:

    print(f'Nitrogen atom energy: {e_atom:5.2f} eV')
    print(f'Nitrogen molecule energy: {e_molecule:5.2f} eV')
    print(f'Atomization energy: {e_atomization:5.2f} eV')

    Nitrogen atom energy:  5.10 eV
    Nitrogen molecule energy:  0.44 eV
    Atomization energy:  9.76 eV

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