Software · User guide

Using Bravais

A walk through the app, roughly in the order you'll meet it: getting a structure on screen, moving around it, then the build and analysis tools. You don't need to read it end to end — skip to whatever you're trying to do.

For installation and downloads, see the Bravais page.

Download the full manual (PDF)

Getting a structure on screen

There are three ways in. The quickest is the sample dropdown on the File tab — it has common metals, semiconductors, oxides and a few teaching structures, so you can start clicking around without a file of your own. To load your own work, use Open and pick a .cif or a VASP POSCAR/CONTCAR. You can also drag a file straight onto the window.

One thing worth knowing about CIF files: Bravais reads the atoms exactly as they're listed and does not expand symmetry. For a P1 file that's everything; for a file that only stores the asymmetric unit you'll see fewer atoms than the full cell. If a structure looks sparse, that's usually why — convert it to P1 first, or load a POSCAR instead.

Moving around

Drag to rotate, scroll to zoom. Click any atom to select it and read off its element, index, and fractional coordinates. The a / b / c buttons snap the camera to look straight down a crystallographic axis, which is the fastest way to check alignment or eyeball a plane. Press R at any point to reset the view if you get lost.

Quad view (Q) splits the window into four panels — top, ortho, left, and a perspective view — so you can see the structure from several angles at once. It's useful for slabs, where a single view hides what's happening along the surface normal.

How it looks: the View tab

The View tab controls rendering and doesn't change the structure itself. The main choices:

• Display mode — ball-and-stick, space-filling, or wireframe.
• Atom size and bonds — scale the atoms, turn bonds on or off (B), and set the distance cut-off that decides what counts as bonded. Periodic bonds, the ones that wrap across the cell edge, have their own toggle because they can clutter the view.
• Colour — by element (the usual CPK-style scheme) or by coordination number, which is handy for spotting under-coordinated surface atoms at a glance.
• Labels (L) — show the element, the atom index, or coordinates next to each atom.
• Unit cell and boundary atoms — draw the cell edges, and optionally show atoms sitting on the cell faces repeated for a fuller picture.
• Lattice plane — overlay a translucent (hkl) plane. Type in the Miller indices, adjust the opacity and colour, and use it to reason about a surface before you cut it.

There's a light and a dark theme; pick whichever is easier on your eyes. None of this is saved into your exported files — it only affects what's on screen.

Supercells

Under Build, set the supercell to repeat the cell along a, b and c (up to 5×5×5). This is purely a viewing and export convenience — it tiles the atoms you already have. Bigger supercells get heavy to render, so step up gradually.

Building a surface slab

This is the part most people come for. From the Build tab, open Create Surface and:

1. Enter the Miller indices (h k l) for the surface you want.
2. Bravais works out the distinct terminations — the inequivalent layers you could cut through — and lists them. Pick one.
3. Choose how many layers thick the slab should be and how much vacuum to add above it.
4. Generate. The slab appears in the 3D view so you can check it before exporting.

Export All writes every termination as its own POSCAR in one go, which saves a lot of clicking when you're screening surfaces for DFT. If you only want the one you're looking at, export the current structure instead.

Adsorbates

With a surface on screen, open the adsorbate tool to drop a molecule onto it — water, CO, CO₂, OH, NH₃, methane and a handful of single atoms are built in with sensible geometry. You control where it sits and how it's tilted and rotated. Adsorbates are tracked separately, so you can add several, edit or remove them individually, and export the surface with everything in place.

Editing atoms

The Edit tab (and its keyboard shortcuts) let you change the structure directly:

• Delete (D) — click atoms to remove them.
• Add (A) — choose an element and place new atoms.
• Move (M) — drag an atom to a new position.

Edits are non-destructive: the first change you make starts a working copy, Ctrl+Z steps back through your history, and you can revert to the structure you loaded. Press Escape to leave an editing mode. The window title flags a structure as modified so you don't forget there are unsaved changes.

Measuring

Switch to the Measure tab or use the number keys: 1 for a distance between two atoms, 2 for an angle across three, 3 for a dihedral across four. Click the atoms in order and the value appears. Measurements stack up in a list so you can take several and clear them when you're done. Selecting a single atom also reports its coordination number, counted with the usual covalent-radius rule.

Analysis tools

The Analysis tab gathers the things that tell you about a structure rather than change it:

• Cell information — lattice parameters, volume, chemical formula and atom count for whatever is currently loaded.
• Radial distribution function — the RDF for the current structure, useful for checking coordination shells and spacing.
• Crystal morphology — a Wulff construction. Give it a surface energy for each (hkl) face and it predicts the equilibrium crystal shape; lower-energy faces grow larger. Only the relative energies matter, so you can compare faces without worrying about absolute units.

Point defects and strain

Also on Build, the defect tool creates a vacancy (remove an atom), a substitution (swap one element for another) or an interstitial (add an atom in a gap). The strain tool applies uniform or biaxial strain by a percentage, which is the quick way to set up a lattice-parameter or epitaxial-strain scan. Both go through the same undo history as manual edits.

NEB paths

The NEB builder interpolates between an initial and a final structure to give you a starting path for a nudged-elastic-band calculation. Choose the number of images and the interpolation: linear moves each atom in a straight line (taking the short way around the cell), while IDPP relaxes that guess so atoms are less likely to overlap on the way — usually the better starting point. The path exports as numbered 00/, 01/ … folders, each with its own POSCAR, ready to hand to VASP.

Comparing two structures

The Compare tab loads a second structure alongside the first and shows them side by side. It's handy for before-and-after — relaxed versus unrelaxed, or two terminations of the same surface.

Exporting

From the File tab you can write the current structure out as a VASP POSCAR, a CIF, or an XYZ file. POSCAR export keeps the coordinate style (Direct or Cartesian) the file came in with, so loading and re-saving round-trips cleanly. Export Image saves a PNG of the current view for slides and figures.

Saving and sharing your session

Save Session (Ctrl+S) writes the whole scene — structure, edits, display settings — to a file you can reopen later with Load Session. Share packs the structure into a link you can send to someone else; opening it rebuilds the structure on their machine. Nothing is uploaded to a server; the data travels inside the link itself.

The AI assistant

Bravais includes an optional assistant that can both answer questions about your structure and actually operate the app for you — set a supercell, cut a surface, add an adsorbate, export, and so on — from a plain-language request. It's off until you open it and paste in your own Anthropic API key, which is stored locally on your machine and sent only to Anthropic to answer your messages. If you'd rather not use it, you can ignore it entirely and nothing else changes.

Learning mode

Under Analysis, Learn Crystallography opens a set of short guided lessons that walk through ideas like lattices, Miller indices and surfaces using the live 3D view. It's aimed at students and anyone new to the subject.

Keyboard shortcuts

Press ? in the app at any time to see this list.

• Drag / Scroll Rotate / zoom the view
• R Reset the view
• Q Toggle quad view
• B Toggle bonds
• L Toggle labels
• 1 / 2 / 3 Measure distance / angle / dihedral
• A / D / M Add / delete / move atoms
• Ctrl+Z Undo the last edit
• Ctrl+S Save session
• Escape Leave the current mode
• ? Show the shortcut list

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Found something that doesn't behave as described, or want a feature? Get in touch from the contact page.