Surface Atlas
← Common surfaces

Low-index SC · Square net

SC(100)

The simple-cubic (100) face is a single square net repeated directly above the layers below it. Its uncluttered geometry separates the ontop, bridge, and fourfold hollow constructions clearly.

Plane
(100)
Layer character
Flat · fourfold symmetry
ASE slab builder
surface

From bulk to facet

How SC(100) is cut

(100) plane cutting through a Simple cubic bulk unit cell
The coloured sheet is one translated member of the (100) plane family; translating it along its normal gives an equivalent termination.

(100)

The plane is perpendicular to one cube axis and parallel to the other two. Every translated member cuts an equivalent square layer of corner-lattice sites.

Bulk lattice
Simple cubic
Plane normal
[100]
What remains
Square net

The plane is drawn through the centre so high-index cuts remain legible. Its orientation is what the indices specify, not its absolute position inside one cell.

Surface geometry

Read the surface from above

surface second layer third layer

L1 is the highest atom-bearing plane, followed by L2 and L3. Support coordinates outside 0–1 are periodic images. The listed Δz describes the supporting atoms, not the marker height. In the interactive model, every numbered site is placed on the same schematic guide plane above the slab; no adsorption distance or energetic ordering is implied.

Top view of SC(100) with numbered adsorption sites
The outlined reference cell has |a1| = 3.3500 Å, |a2| = 3.3500 Å, and γ = 90.00° for the Po slab used in the drawing. Fractional coordinates mean r∥ = ua1 + va2.
  1. ontop1-fold

    Directly above one outermost atom.

    (u,v) = (0, 0)s = s₁ · support shell: mean Δz = +0.000 Å from L1

    Projection of the L1 atom at (0, 0).

    Not named in ASE
  2. bridge2-fold

    Halfway between nearest neighbours along a square-net edge.

    (u,v) = (1/2, 0)s = (s₁ + s₂) / 2 · support shell: mean Δz = +0.000 Å from L1

    Periodic midpoint of L1 (0, 0) and L1 (1, 0).

    Not named in ASE
  3. fourfold hollow4-fold

    At the centre of a square of four surface atoms.

    (u,v) = (1/2, 1/2)s = (Σᵢ sᵢ) / 4 · support shell: mean Δz = +0.000 Å from L1

    Least-squares centroid of the 4-atom projected shell: L1 (0, 0), L1 (1, 0), L1 (0, 1), L1 (1, 1).

    Not named in ASE

Interactive model

Rotate the slab

Sites share a schematic display height · drag to rotate · hover for names

Building the model…

Below the top layer

Why the sites are different

Successive layers have AA registry, so every deeper atom projects onto an outermost atom rather than into the square hollow.

Side profile of SC(100) showing its first repeating atomic layers
Side profile showing one compact stacking repeat. The dashed line follows the macroscopic surface plane.
Layer registry of SC(100)
Layer registry viewed from above; opacity increases towards the surface.

Cell

Geometry at a glance

For a cubic lattice, \(d_{100}=a\). The primitive surface cell is a square of side \(a\) containing one lattice site.

A site name describes the ideal starting geometry. Relaxation can move an adsorbate away from it.

Practical model

Build it with ASE

The builder creates the slab. Sites marked ASE keyword can be passed directly as a named position; ASE source marks current but inconsistently documented support. Other sites require explicit Cartesian coordinates converted from the fractional construction above.

from ase.build import bulk, surface

po = bulk("Po", "sc", a=3.35, cubic=True)
slab = surface(po, (1, 0, 0), 6, vacuum=10)
Things that are easy to misread
  • Importing the alternating layer registry of BCC(100) into the AA-stacked SC face.
  • Calling the square centre a threefold hollow.