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Supported File Formats

ASE automatically detects file formats using three methods:

  1. Extension - File extension (e.g., .xyz, .cif)
  2. Filename pattern - Glob matching (e.g., *POSCAR*, GEOMETRY.OUT)
  3. Magic bytes - Content signature detection

Format Detection Priority

1. Filename pattern match (glob)
2. File extension match
3. Magic bytes detection (reads first ~50KB)
4. Fallback to extension as format name

Quick Reference

Format Extension Filename Pattern Magic Detection
extxyz .xyz — —
cif .cif — —
vasp .poscar *POSCAR*, *CONTCAR* —
traj .traj — ✓
json .json — —
pdb .pdb — —

All Formats by Category

Molecular Formats

Format Ext Glob Magic Description
extxyz xyz — — Extended XYZ file
xyz — — — XYZ file (plain)
cif cif — — Crystallographic Information File
proteindatabank pdb — — Protein Data Bank
mol — — — MDL Molfile
sdf — — — SDF format
cjson cjson — — Chemical JSON
gen — — — DFTB+ GEN format

ASE Native

Format Ext Glob Magic Description
traj traj — - of UlmASE-Trajectory ASE trajectory
json json — — ASE JSON database
db — — — ASE SQLite database
bundletrajectory — — — ASE bundle trajectory

VASP

Format Ext Glob Magic Description
vasp poscar *POSCAR*, *CONTCAR*, *CENTCAR* — POSCAR/CONTCAR
vasp-out — *OUTCAR* — OUTCAR file
vasp-xdatcar — *XDATCAR* — XDATCAR file
vasp-xml — *vasp*.xml — vasprun.xml

Quantum ESPRESSO

Format Ext Glob Magic Description
espresso-in pwi — *\n&system, *\n&SYSTEM QE input
espresso-out pwo, out — *Program PWSCF QE output

Gaussian

Format Ext Glob Magic Description
gaussian-in com, gjf — — Gaussian input
gaussian-out log — *Entering Gaussian System Gaussian output

ORCA

Format Ext Glob Magic Description
orca-output — — * O R C A * ORCA output

FHI-aims

Format Ext Glob Magic Description
aims in — — FHI-aims geometry
aims-output — — *Invoking FHI-aims ... FHI-aims output

CASTEP

Format Ext Glob Magic Description
castep-castep castep — — CASTEP output
castep-cell cell — — CASTEP geometry
castep-geom geom — — CASTEP trajectory
castep-md md — — CASTEP MD file
castep-phonon phonon — — CASTEP phonon

CP2K

Format Ext Glob Magic Description
cp2k-dcd dcd — — CP2K DCD file
cp2k-restart restart — — CP2K restart

GPAW

Format Ext Glob Magic Description
gpaw-out — — * ___ ___ ___ _ _ _ GPAW text output
gpw — — - of UlmGPAW GPAW restart file

ABINIT

Format Ext Glob Magic Description
abinit-gsr — *o_GSR.nc — ABINIT GSR file
abinit-in — — *znucl * ABINIT input
abinit-out — — *.Version * of ABINIT ABINIT output

LAMMPS

Format Ext Glob Magic Description
lammps-data — — — LAMMPS data file
lammps-dump-text — — ITEM: TIMESTEP (regex) LAMMPS text dump
lammps-dump-binary — — — LAMMPS binary dump

NWChem

Format Ext Glob Magic Description
nwchem-in nwi — — NWChem input
nwchem-out nwo — *Northwest Computational... NWChem output

TURBOMOLE

Format Ext Glob Magic Description
turbomole — coord $coord TURBOMOLE coord
turbomole-gradient — gradient $grad TURBOMOLE gradient

Other DFT Codes

Format Ext Glob Magic Description
dftb — — Geometry DFTB+ input
elk — GEOMETRY.OUT — ELK output
exciting — input.xml, INFO.out — exciting
siesta-xv — *.XV — Siesta XV file
octopus-in — inp — Octopus input
onetep-out — — *Linear-Scaling Ab Initio* ONETEP output
qbox — — *:simulation xmlns: QBOX output

Crystal Formats

Format Ext Glob Magic Description
crystal f34, 34 f34, 34 — Crystal fort.34
xsf — — *\nCRYSTAL, *\nATOMS, etc. XCrySDen
cube cube — — Gaussian CUBE
struct — — — WIEN2k structure
res shelx — — SHELX format

Visualization/Export

Format Ext Glob Magic Description
png — — — PNG image
eps — — — Encapsulated PostScript
pov — — — POV-Ray
gif — — — GIF animation
mp4 — — — MP4 video
html — — — X3DOM HTML
x3d — — — X3D format

Other

Format Ext Glob Magic Description
cfg — — — AtomEye configuration
gromacs gro — — Gromacs coordinates
gromos g96 — — Gromos96 geometry
dlp4 config *CONFIG* — DL_POLY_4 CONFIG
dlp-history — HISTORY — DL_POLY HISTORY
eon con — — EON CON file
gpumd — xyz.in — GPUMD input
magres — — — MAGRES NMR data
netcdftrajectory — — CDF AMBER NetCDF
v-sim ascii — — V_Sim ascii
rmc6f rmc6f — — RMCProfile

Compression Support

ASE automatically handles compressed files with .gz, .bz2, .xz extensions.