# Perform a geomtry optimization
from ase import Atoms, PickleTrajectory, read
from ase.optimize.lbfgs import LBFGS, LBFGSLineSearch
from gpaw import GPAW, Mixer, MixerSum, ConvergenceError, PoissonSolver
from gpaw.poisson import PoissonSolver
from gpaw.eigensolvers.rmm_diis import RMM_DIIS
ps = PoissonSolver(nn='M', relax='GS', eps=1e-9)
es = RMM_DIIS(keep_htpsit=False)

# Makes Python traceback appear only on the root processor
import sys
from gpaw.mpi import world
from ase.utils import devnull
if world.rank != 0:
    sys.stderr = devnull

epsilon = 0.02 # small perturbation

a = 4.08
bulk = Atoms('Au4', positions=((0, 0 ,0),
                               (0.5, 0.5, 0),
                               (0.5, epsilon, 0.5),
                               (0, 0.5, 0.5)), pbc=True)

bulk.set_cell((a,a,a), scale_atoms=True)
bulk = bulk.repeat((1, 1, 1))
calc = GPAW(h=0.16,
            maxiter=200,
            mode = 'fd',
            poissonsolver = ps,
            nbands = 30,
            spinpol = False,
            xc = 'LDA',
            width = 0.01,
            mixer = Mixer(0.10, 5, 100.0), 
            # mixer = MixerSum(0.10, 5, 100.0), # spinpol = True
            eigensolver = es,
            parallel = {'buffer_size':2048},
            txt = 'Au_bulk.out')

bulk.set_calculator(calc)
# spinpol = True
# magmom = 2.0
# mms = [magmom for i in range(len(bulk))]
# bulk.set_initial_magnetic_memonts(mms)

world.barrier() # make sure things are synchronized

mode = 'w'
traj = PickleTrajectory('qn.traj', mode, bulk)
relax = LBFGS(bulk, logfile = 'qn.log', trajectory = traj, restart= 'qn.pckl')
relax.attach(lambda: calc.write('Au_bulk.%d.hdf5' % relax.nsteps))
relax.run(fmax=0.05, steps=2)