Choose an input route
| Route | What to check |
|---|---|
| New structure | Set the cell lengths and angles, species, and atom positions explicitly. |
| CIF | Check occupancies, disorder, fractional coordinates, and whether the intended cell is primitive or conventional. |
| POSCAR / VASP | Verify the scale factor, element ordering, and Direct versus Cartesian positions. |
| XSF / XYZ / PDB | Confirm that the file contains a usable simulation cell; isolated coordinates alone do not define periodicity. |
| Quantum ESPRESSO input/output | Check the imported cell and whether the positions correspond to the intended ionic step. |
| Materials Project | Inspect source identity, composition, cell convention, and the suitability of the database structure for your question. |
Import a file
- Select the destination project.
- Use Add structure / Import, or drop one supported structure file into the workspace.
- Inspect the structure record, formula, number of atoms, and cell.
- Rotate and repeat the cell visually to find misplaced atoms or unexpected neighbors.
- Resolve parser warnings or partial occupancies before using the model for an ordered QE calculation.
Fractional and Cartesian coordinates
Fractional coordinates locate an atom by a combination of the cell vectors: r = f1 a + f2 b + f3 c. Cartesian coordinates specify x, y, and z in a length unit. A value of 0.5 in a fractional field is half a lattice vector, not half an angstrom.
For tilted cells, cell length and perpendicular vacuum thickness are different. Check the full cell geometry instead of assuming the c vector points along the Cartesian z axis.