--- title: "CIF Viewer Online: 3D Unit Cell and Supercell | MolDraw" url: https://www.moldraw.com/tools/free-chem-tools/cif-viewer-online.html description: "Free CIF viewer: open a crystal .cif to see the 3D unit cell or supercell with bonds, polyhedra, space group, formula and density (NaCl: 2.163 g/cm³)." lang: en publisher: Scidart Academy generated: 2026-10-31 --- [MolDraw](https://www.moldraw.com/) › [Chemistry tools](https://www.moldraw.com/tools/) › CIF Viewer Online # CIF Viewer Online **In short:** Open a crystal CIF and see the full unit cell in 3D: the symmetry operations fill the cell, and you can grow it into a supercell, show bonds and polyhedra, and read the space group, formula and density. It is free and runs in your browser. **Quick answer:** Press **NaCl**. Two sites and the 192 operations of Fm-3m fill the cubic cell (a = 5.6402 Å) with **4 Na + 4 Cl** (Z = 4). The calculated density is **2.163 g/cm³**. Set the repeats to 2 × 2 × 2 and tick Polyhedra to see the NaCl₆ octahedra. Open .cif file Examples: **Or paste CIF text** Open a CIF or press an example. The unit cell appears here. Drag to rotate, scroll or pinch to zoom, double-click to reset. Repeat a Repeat b Repeat c Style Bonds and ionic contacts Atoms on cell faces Cell edges and a, b, c axes Polyhedra Spin Click an atom to see its site label and fractional coordinates. ### Export the drawn block (unit cell or supercell) XYZ is extended XYZ (lattice in the comment line); POSCAR is VASP 5 with Direct coordinates. Each atom is written once (no face copies). ## How to view a CIF file in 3D 1. Press **Open .cif file**, or paste the text and press **View crystal**. Or press an example. 2. Set **Repeat a, b, c**. 1 × 1 × 1 is the unit cell; 2 × 2 × 2 is a supercell with 8 cells. 3. Pick **Ball and stick**, **Spacefill**, **Sticks** or **Wire**. 4. Tick **Polyhedra** and pick the centre element to see coordination polyhedra. 5. Read the crystal data table, then press **Save PNG**, **Download .xyz** or **Download POSCAR**. ## From a CIF to the picture A **CIF** lists the cell (a, b, c, α, β, γ), the space group with its symmetry operations, and only the symmetry-unique atom sites in fractional coordinates. The viewer applies every operation to every site, wraps the results into the cell and merges copies closer than 0.1 Å. This is the same reader as MolDraw's [CIF to XYZ and POSCAR converter](https://www.moldraw.com/tools/free-chem-tools/cif-to-xyz-poscar-converter.html) and the Crystal View in the editor. ### Bonds, contacts and polyhedra Links are found with periodic images, so bonds that cross a cell face are kept. A **bond** is drawn when the distance is below 1.15 × (r₁ + r₂), with covalent radii from Cordero et al. (2008). Group 1 and 2 cations (Na, K, Mg, Ca, Sr…) get dashed **ionic contacts** to their first shell of anions instead. Metal–metal pairs get no links. A **polyhedron** joins the non-metal neighbours of a centre atom, and is drawn only when all of them are inside the drawn block. ### Crystal data `ρ = Z × M / (N_A × V) N_A = 6.02214076 × 10²³ mol⁻¹, 1 ų = 10⁻²⁴ cm³` The crystal system follows from the space-group number (1–2 triclinic, 3–15 monoclinic, 16–74 orthorhombic, 75–142 tetragonal, 143–167 trigonal, 168–194 hexagonal, 195–230 cubic). Z is the number of formula units in the cell, found from the atom counts. If the CIF gives `_exptl_crystal_density_diffrn`, it is shown next to the calculated value. ## Limitations - Partial occupancy (disorder) is not drawn as such: every listed site is drawn as a full atom. The density uses the occupancies. - Hydrogens missing from the CIF are not added, so the density of an organic crystal without H is too low. - The conventional cell is shown; the tool does not reduce to a primitive cell or change the setting. - Bonds come from distances only, so very long or unusual bonds may be missed and close contacts may be drawn as bonds. Bond orders are not shown. - Only the first data block with a cell and atom sites is read. Magnetic, modulated and protein (mmCIF) files are not supported here; use the [PDB viewer](https://www.moldraw.com/tools/free-chem-tools/pdb-viewer-online.html) for proteins. ## Frequently asked questions ### How do I view a CIF file online? Press Open .cif file and pick the file, or paste its text and press View crystal. The viewer applies the symmetry operations to the listed sites, fills the unit cell and draws it in 3D with the cell edges. Nothing is uploaded. ### Why does the NaCl unit cell show 27 atoms when it holds 8? The conventional NaCl cell holds 4 Na and 4 Cl. Atoms on faces, edges and corners are shared with neighbouring cells, so the picture also draws their copies on the far faces: 14 Na + 13 Cl = 27 spheres. Untick Atoms on cell faces to draw each atom once. ### How is the density calculated? Density = mass of the cell contents / (Avogadro constant × cell volume). For NaCl: 4 × 58.44 g/mol / (6.022 × 10²³ mol⁻¹ × 179.43 × 10⁻²⁴ cm³) = 2.163 g/cm³. Partly occupied sites count with their occupancy. ### When are polyhedra drawn? Tick Polyhedra and pick the centre element (for example Ti in rutile). A polyhedron is drawn around each centre atom whose whole first coordination shell (4 or more non-metal neighbours) is inside the drawn block. Use a 2 × 2 × 2 block to see more complete polyhedra. ### Can it open protein mmCIF files? No. This viewer is for small-molecule and inorganic crystal CIFs with a unit cell and fractional coordinates. Open protein mmCIF files from the PDB in the PDB viewer. ## Related chemistry tools [CIF to XYZ and POSCAR Converter](https://www.moldraw.com/tools/free-chem-tools/cif-to-xyz-poscar-converter.html)[Bragg's Law and XRD Calculator](https://www.moldraw.com/tools/free-chem-tools/braggs-law-xrd-calculator.html)[PDB Viewer Online](https://www.moldraw.com/tools/free-chem-tools/pdb-viewer-online.html)[Crystal View: CIF unit cells in 3D](https://www.moldraw.com/blog/crystal-view-plugin-cif-unit-cell-3d.html)[3D Molecular Model Viewer](https://www.moldraw.com/tools/free-chem-tools/3d-molecular-model-viewer.html)[Point Group Finder](https://www.moldraw.com/tools/free-chem-tools/point-group-finder.html) Last updated: October 30, 2026