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.

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