Unit Cell Editor

ACoord provides tools for editing crystal unit cells and generating supercells.

Unit Cell Basics

A unit cell is defined by:

• Lengths: a, b, c (in Angstroms)
• Angles: α, β, γ (in degrees)

Editing Lattice Parameters

1. Open Lattice panel in the sidebar
2. Enter values for a, b, c, α, β, γ
3. Check/uncheck Scale atoms with lattice
   • Checked: atoms move with cell (preserves fractional coordinates)
   • Unchecked: atoms stay fixed (preserves Cartesian coordinates)
4. Click Apply Lattice

Click Remove Lattice to remove the unit cell from the structure.

Supercell Display

1. Open Lattice panel
2. Enter supercell dimensions (Nx, Ny, Nz)
3. Click Apply Supercell

The display shows periodic images of atoms. Use cases include defect calculations, surface models, and visualization of periodicity.

Centering Atoms

1. Click Center At Cell button in the Lattice panel
2. Confirm the operation
3. All atoms are translated so the geometric center aligns with the cell center

This operation can be undone with Ctrl+Z.

Unit Cell Style

Customize appearance in the Size & Style panel:

• Color: Change unit cell edge color
• Thickness: Adjust line thickness (0.5-6)
• Line style: Solid or dashed

Crystal Systems

ACoord supports all 7 crystal systems:

System	Parameters	Example
Cubic	a=b=c, α=β=γ=90°	Si, NaCl
Tetragonal	a=b≠c, α=β=γ=90°	TiO₂
Orthorhombic	a≠b≠c, α=β=γ=90°	FeB
Hexagonal	a=b≠c, α=β=90°, γ=120°	ZnO
Rhombohedral	a=b=c, α=β=γ≠90°	α-Al₂O₃
Monoclinic	a≠b≠c, α=γ=90°≠β	SiO₂
Triclinic	a≠b≠c, α≠β≠γ	K₂Cr₂O₇