Tutorial for using Fair Chemistry models to relax NEBs

Tutorial for using Fair Chemistry models to relax NEBs#

from ase.optimize import BFGS
from ase.io import read

from fairchem.applications.cattsunami.core.autoframe import interpolate
from fairchem.applications.cattsunami.core import OCPNEB
from fairchem.core.models.model_registry import model_name_to_local_file

#Optional
from x3dase.x3d import X3D
import matplotlib.pyplot as plt
import os

Set up inputs#

Shown here are the values used consistently throughout the paper.

fmax = 0.05 # [eV / ang]
delta_fmax_climb = 0.4 # this means that when the fmax is below 0.45 eV/Ang climbing image will be turned on
k = 1 # you may adjust this value as you see fit
cpu = True # set to False if you have a GPU


# NOTE: Change the checkpoint path to locally downloaded files as needed
checkpoint_path = model_name_to_local_file('EquiformerV2-31M-S2EF-OC20-All+MD', local_cache='/tmp/fairchem_checkpoints/')

If you have your own set of NEB frames#

"""
Load your frames (change to the appropriate loading method)
The approach uses ase, so you must provide a list of ase.Atoms objects
with the appropriate constraints.
"""
cwd = os.getcwd()
path_ = os.path.abspath(os.path.join(cwd, os.pardir, os.pardir))
path_ = os.path.join(path_, "src", "fairchem", "applications", "cattsunami", "tutorial", "sample_traj.traj")
frame_set = read(path_, ":")[0:10] # Change to the path to your atoms of the frame set

neb = OCPNEB(
    frame_set,
    checkpoint_path=checkpoint_path,
    k=k,
    batch_size=8, # If you get a memory error, try reducing this to 4
    cpu = cpu,
)
optimizer = BFGS(
    neb,
    trajectory=f"your-neb.traj",
)
conv = optimizer.run(fmax=fmax + delta_fmax_climb, steps=200)
if conv:
    neb.climb = True
    conv = optimizer.run(fmax=fmax, steps=300)

If you have a proposed initial and final frame#

You may use the interpolate function we implemented which is very similar to idpp but not sensative to periodic boundary crossings. Alternatively you can adopt whatever interpolation scheme you prefer. The interpolate function lacks some of the extra protections implemented in the interpolate_and_correct_frames which is used in the CatTSunami enumeration workflow. Care should be taken to ensure the results are reasonable.

IMPORTANT NOTES:

  1. Make sure the indices in the initial and final frame map to the same atoms

  2. Ensure you have the proper constraints on subsurface atoms

"""
Load your initial and frames (change to the appropriate loading method)
The approach uses ase, so you must provide ase.Atoms objects
with the appropriate constraints (i.e. fixed subsurface atoms).
"""
initial_frame = read("path-to-your-initial-atoms.traj")
final_frame = read("path-to-your-final-atoms.traj")
num_frames = 10 # you may change this to whatever you like

frame_set = interpolate(initial_frame, final_frame, num_frames)

neb = OCPNEB(
    frame_set,
    checkpoint_path=checkpoint_path,
    k=k,
    batch_size=8, # If you get a memory error, try reducing this to 4
    cpu = cpu,
)
optimizer = BFGS(
    neb,
    trajectory=f"your-neb.traj",
)
conv = optimizer.run(fmax=fmax + delta_fmax_climb, steps=200)
if conv:
    neb.climb = True
    conv = optimizer.run(fmax=fmax, steps=300)

Visualize the results#

optimized_neb = read(f"your-neb.traj", ":")[-1*nframes:]

es  = []
for frame in optimized_neb:
    frame.set_calculator(calc)
    es.append(frame.get_potential_energy())

# Plot the reaction coordinate

es = [e - es[0] for e in es]
plt.plot(es)
plt.xlabel("frame number")
plt.ylabel("relative energy [eV]")
plt.title(f"Ea = {max(es):1.2f} eV")
plt.savefig("reaction_coordinate.png")

# Make an interative html file of the optimized neb trajectory
x3d = X3D(optimized_neb)
x3d.write("your-neb.html")
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