Datasets:
File size: 2,380 Bytes
3dee505 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 | {
"description": "Given the INCAR, POSCAR summary, and OUTCAR excerpt below, diagnose why structural relaxation diverges.",
"diagnosis_hint": "Two compounding issues: (1) POTIM=1.0 is far too large - the default 0.5 or even 0.1-0.3 would be safer; (2) starting from the wrong phase (cubic instead of orthorhombic) means initial forces are huge. Fix: reduce POTIM to 0.1-0.2, or better yet, start from the orthorhombic Pnma structure. For unknown ground-state structures, use a conservative POTIM with IBRION=1 (RMM-DIIS) which handles large steps better than conjugate gradient.",
"incar": {
"EDIFF": 1e-06,
"EDIFFG": -0.02,
"ENCUT": 450,
"IBRION": 2,
"ISIF": 3,
"ISMEAR": 0,
"ISPIN": 1,
"NSW": 300,
"POTIM": 1.0,
"PREC": "Accurate",
"SIGMA": 0.05,
"SYSTEM": "Perovskite_CsPbI3_cubic",
"_comment": "BUG: POTIM=1.0 is too large for this system. Combined with an initial structure that has the cubic phase (high-T) instead of the actual ground-state orthorhombic phase, the forces are large and POTIM=1.0 causes atoms to overshoot drastically. Each ionic step the structure bounces back and forth, never settling."
},
"key_observation": "Energy increases from step 1 to step 4, forces explode from 2.3 to 48 eV/A, volume swings wildly. By step 5, VASP encounters a fatal bracketing error. The ionic step is too aggressive.",
"outcar_excerpt_ionic_steps": [
"--- step 1: E= -19.23456 max_force= 2.341 volume= 248.9",
"--- step 2: E= -17.89123 max_force= 5.672 volume= 275.3",
"--- step 3: E= -12.34567 max_force= 12.891 volume= 312.1",
"--- step 4: E= +8.45231 max_force= 48.234 volume= 189.2",
"--- step 5: ZBRENT: fatal internal error",
" please rerun with smaller POTIM, or copy CONTCAR to POSCAR and continue"
],
"poscar_summary": {
"counts": [
1,
1,
3
],
"lattice_a": 6.289,
"note": "Cubic CsPbI3 is the high-temperature phase; ground state is orthorhombic Pnma. Starting from cubic with ISIF=3 requires large atomic displacements and cell shape changes.",
"species": [
"Cs",
"Pb",
"I"
],
"system": "CsPbI3 cubic Pm-3m (high-T phase, NOT ground state)",
"total_atoms": 5
},
"root_cause": "potim_too_large_and_bad_initial_structure",
"task": "relax_divergence_diagnosis"
}
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