"""
amorphgen.pipeline.melt_cell
-----------------------------
Stage 3 – Heat the structure from T_start to T_end via a temperature ramp.
Ensemble is configurable: NPT (default) or NVT.
"""
from __future__ import annotations
from copy import deepcopy
from ase.io import read, write
from ase.md.velocitydistribution import MaxwellBoltzmannDistribution
from ..utils import (get_calculator, make_cubic,
build_md_dynamics, attach_outputs, merge_config)
from ..configs import DEFAULT_CONFIG
[docs]
def run(atoms_or_file, cfg_override=None, calc=None, **kwargs):
"""
Heat the structure from T_start -> T_end.
Parameters
----------
atoms_or_file : str or ase.Atoms
cfg_override : dict, optional
calc : ASE calculator, optional
Returns
-------
ase.Atoms — melted structure at T_end
"""
global_cfg = merge_config(DEFAULT_CONFIG, cfg_override)
cfg = global_cfg["melt"]
ensemble = cfg.get("ensemble", "NPT").upper()
if isinstance(atoms_or_file, str):
atoms = read(atoms_or_file)
print(f"[Stage 3] Loaded from {atoms_or_file}")
else:
atoms = deepcopy(atoms_or_file)
print("[Stage 3] Using provided Atoms object")
# Optional cubic reshape
if cfg.get("make_cubic", True):
atoms = make_cubic(atoms)
print("[Stage 3] Cell reshaped to cubic")
logfile = cfg.get("log_file", "stage3_melt.log")
trajfile = cfg.get("traj_file", "stage3_melt_traj.xyz")
# Frame-level resume: continue a walltime-killed ramp from the last
# trajectory frame (momenta included); the ramp position is recovered
# via ramp_resume_position below. The legacy filename lets a run
# interrupted under a pre-rename AmorphGen still resume after upgrade.
from ..utils.common import (resume_md_stage, needs_velocity_init,
ramp_resume_position)
ck_atoms, elapsed = resume_md_stage(trajfile, kwargs.get("resume"), "3",
legacy_trajfile="stage3_melt.xyz")
if ck_atoms is not None:
atoms = ck_atoms
if calc is None:
from ..utils.common import resolve_device
device = resolve_device(global_cfg.get("device", "cuda"))
calc = get_calculator(
model=global_cfg.get("model", "mace-mpa-0"),
device=device,
model_path=global_cfg.get("model_path"),
)
atoms.calc = calc
T_start = cfg["T_start"]
if needs_velocity_init(atoms, elapsed):
MaxwellBoltzmannDistribution(atoms, temperature_K=T_start)
dyn = build_md_dynamics(
atoms, ensemble=ensemble, T=T_start,
timestep=cfg.get("timestep", 1.0),
friction=cfg.get("friction", 0.01),
ttime=cfg.get("ttime", 25.0),
npt_method=cfg.get("npt_method", "berendsen"),
taup_factor=cfg.get("taup_factor", 10.0),
compressibility_GPa=cfg.get("compressibility_GPa", 100.0),
)
logger, traj = attach_outputs(dyn, atoms, logfile, trajfile,
fmt=global_cfg.get("traj_format", "extxyz"),
append=elapsed > 0)
# Temperature ramp
T_end = cfg["T_end"]
T_step = abs(cfg.get("T_step", 100))
timestep_fs = cfg.get("timestep", 1.0)
# Allow rate (K/ps) to auto-calculate steps_per_T
rate = cfg.get("rate")
if rate is not None:
if T_step == 0:
raise ValueError("T_step cannot be 0 when rate is specified.")
steps = int(round(T_step / (rate * timestep_fs / 1000)))
steps = max(steps, 1)
else:
steps = cfg.get("steps_per_T", 1000)
target_temps = list(range(T_start, T_end + T_step, T_step))
actual_rate = T_step / (steps * timestep_fs / 1000)
from ..utils.common import compute_density_gcm3
density = compute_density_gcm3(atoms)
print(f"[Stage 3] {ensemble} heat ramp: {T_start} -> {T_end} K "
f"(+{T_step} K, {steps} steps each, {actual_rate:.1f} K/ps) "
f"density={density:.2f} g/cm3")
# Recover the ramp position on resume: k0 full segments done, offset
# steps into segment k0 (see ramp_resume_position for the
# elapsed==total edge semantics).
k0, offset = ramp_resume_position(elapsed, steps, len(target_temps))
for idx, T in enumerate(target_temps):
if idx < k0:
continue
dyn.set_temperature(temperature_K=T)
run_steps = steps - offset if idx == k0 else steps
note = f" (resumed, {run_steps} steps left)" if (idx == k0 and offset) else ""
print(f" -> T = {T:5d} K{note}")
dyn.run(run_steps)
logger.close()
traj.close()
out_xyz = cfg.get("output_xyz", "stage3_melted.xyz")
write(out_xyz, atoms, format="extxyz")
print(f"[Stage 3] Saved -> {out_xyz}\n")
return atoms