CogLabThe Cognition Lab

Physics simulations

Materials Atlas · physics workbench

Model. Compare. Investigate.

Work from molecular geometry, crystal structure, processing conditions or a material stack. Inspect the physics, compare calculated results, and turn uncertainty into the next research question.

01 Define the system02 Review the method03 Calculate & check04 Compare & decide
Define your calculation

Neutral defects in a crystal

Construct a vacancy or interstitial, relax its local geometry and account for formation energy against an explicit chemical potential.

Scientific inputs
Method scope & sources

Monatomic neutral defects under a specified Lennard–Jones model, with immutable before/after structures.

  • Explicit pair-potential and chemical-potential reference
  • Neutral defects only; no electronic charge corrections
  • Finite supercells and local relaxation need size and convergence checks

ASE structure manipulation ↗

Calculated result

Neutral vacancy · periodic pair model

Model calculation
Neutral defect formation energy0.081091eV/defect
Bulk supercell energy-2.2071eV/cell
Defect supercell energy-2.0442eV/cell
Supplied reservoir chemical potential-0.081744eV/atom
Energy change on atomic relaxation-0.00065264eV/cell
Final maximum force0.00056632eV/Å
Cell energy (eV/cell)
-2.04360-2.04380.75-2.04391.5-2.04412.25-2.04423
Recorded optimization step
Defect relaxation
Recorded optimization step: 0 · Cell energy: -2.0436 eV/cell

Interpret the result

  • Neutral defect with explicit atom-count change and compatible total-cell energy normalization.
  • Identical pair potential and periodic cell for bulk and defect; atom positions may relax while cell vectors remain fixed.
  • Formation energy uses E_defect − E_bulk − Σ ΔN μ; no Fermi-level or charged-cell correction is included.

Uniform Lennard–Jones bonding is an explicitly supplied model; an element label does not establish defect accuracy for real chemistry.

The cell is fixed and periodically repeats the defect. Finite-size interactions and chemical-potential uncertainty require separate convergence and evidence.

The chemical potential is user-supplied with a declared reference; textual provenance is not an independent verification of that reservoir.

Meeting a force threshold establishes stationarity, not a stable minimum. High-symmetry interstitials may be saddle points; a defect Hessian or perturbed multi-start relaxation is needed to test stability.

Numerical checks & provenance
Declared atom-count change0 ≤ 1E-12 atoms
Stoichiometric formation-energy accounting0 ≤ 1E-10 eV
Independent energy derivative versus atomic force2.1582E-11 ≤ 0.0001 eV/Å

Passing these checks verifies the stated numerical properties. Agreement with experiment requires a separate, condition-matched comparison.

Input SHA-256: e34b8b12305f78febebea5f6b26dd49134b7028a46c0c95937d60ccfd5d96daf
Runner SHA-256: f27376d0f80371a1da4c926f1a21d43d841802e9f87bac7e876738ea78181e3d
atlas 1 · python 3.14.10 · numpy 2.5.4 · scipy 1.18.1 · defects_sha256 0245994c7e3ad6257a618393814b9c3c319125205a00b1751003d8efb60afa41 · ase 3.29.0
Calculated 11/12/2026, 2:07:51 AM · 0.074023 s

Test the explanation

Compare a numerical refinement or a different physical assumption. Agreement within one model does not establish agreement with experiment.

Build the investigation

Bring the observable, conditions and result into a research plan with competing hypotheses and a test that can distinguish them.

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