from ase.build import fcc100, add_adsorbate
from ase.constraints import FixAtoms
from ase.calculators.emt import EMT
from ase.dimer import DimerControl, MinModeAtoms, MinModeTranslate


def test_dimer_method():
    # Set up a small "slab" with an adatoms
    atoms = fcc100('Pt', size = (2, 2, 1), vacuum = 10.0)
    add_adsorbate(atoms, 'Pt', 1.611, 'hollow')

    # Freeze the "slab"
    mask = [atom.tag > 0 for atom in atoms]
    atoms.set_constraint(FixAtoms(mask = mask))

    # Calculate using EMT
    atoms.calc = EMT()
    atoms.get_potential_energy()

    # Set up the dimer
    d_control = DimerControl(initial_eigenmode_method = 'displacement', \
                             displacement_method = 'vector', logfile = None, \
                             mask = [0, 0, 0, 0, 1])
    d_atoms = MinModeAtoms(atoms, d_control)

    # Displace the atoms
    displacement_vector = [[0.0]*3]*5
    displacement_vector[-1][1] = -0.1
    d_atoms.displace(displacement_vector = displacement_vector)

    # Converge to a saddle point
    dim_rlx = MinModeTranslate(d_atoms, trajectory = 'dimer_method.traj', \
                               logfile = None)
    dim_rlx.run(fmax = 0.001)

    # Test the results
    tolerance = 1e-3
    assert(d_atoms.get_barrier_energy() - 1.03733136918 < tolerance)
    assert(abs(d_atoms.get_curvature() + 0.900467048707) < tolerance)
    assert(d_atoms.get_eigenmode()[-1][1] < -0.99)
    assert(abs(d_atoms.get_positions()[-1][1]) < tolerance)
