Minimization

Local minimization relaxes a structure to the nearest potential energy minimum using one of several optimization algorithms.

To run a minimization, set job to minimization in the [Main] section:

[Main]
job = minimization

[Optimizer]
opt_method = lbfgs
converged_force = 0.01
max_iterations = 1000

Or programmatically via rgpycrumbs:

from rgpycrumbs.eon.helpers import write_eon_config

config = {
    "Main": {"job": "minimization"},
    "Optimizer": {"opt_method": "lbfgs", "converged_force": 0.01},
}
write_eon_config(config, Path("config.ini"))

The optimizer settings control convergence. See Optimizer for the full list of available optimizers and their parameters.

Tip

Enable [Debug] write_movies = true (and optionally write_deprecated_outs = true) so rgpycrumbs eon plt-min can build energy profiles, 2D landscapes, and convergence panels. For two endpoints, use separate landscape plots (one --job-dir / --label each). See LJ cluster minimization (built-in potential) and Real systems for documentation.

Optimizer selection

Optimizer	Best for	Key parameter
LBFGS (default)	Most minimizations, fast convergence near minima	lbfgs_memory (default 20)
FIRE	Systems far from equilibrium, robust for bad initial guesses	time_step
CG	Large systems where LBFGS memory is a concern	cg_line_search
QuickMin	Simple dynamics-based relaxation	time_step
SD	Debugging, guaranteed descent direction	sd_alpha

Convergence

The minimization converges when the force criterion is met. Three metrics are available via convergence_metric:

• norm (default): root-mean-square force across all free atoms

• max_atom: maximum force on any single atom

• max_component: maximum force component (x, y, or z)

Refinement

For paths far from the minimum, a two-stage optimization can be faster: start with a robust optimizer (QuickMin or FIRE) and switch to LBFGS after the forces drop below a threshold.

[Optimizer]
opt_method = fire

[Refine]
opt_method = lbfgs
threshold = 0.5

This runs FIRE until the max force drops below 0.5 eV/A, then switches to LBFGS for final convergence.

Output

The minimization writes:

• min.con: the minimized structure

• results.dat: energy, force calls, convergence status

With write_movies = true (in [Debug]), minimization.con is written as a concatenated structure movie (one frame per iteration). Each frame stores structured JSON metadata on line 2 via readcon-core, including energy, frame_index, step_size, and convergence.

Set write_deprecated_outs = true in [Debug] to also emit the legacy minimization.dat sidecar during the compatibility window.

Configuration