Surface Atlas
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Low-index BCC · Rectangular net

BCC(110)

BCC(110) is the densest BCC face. Zig-zag rows pack more closely than on BCC(100), while the rectangular cell retains two inequivalent bridge directions.

Plane
(110)
Layer character
Flat · close packed for BCC
ASE slab builder
bcc110

From bulk to facet

How BCC(110) is cut

(110) plane cutting through a Body-centred cubic bulk unit cell
The coloured sheet is one translated member of the (110) plane family; translating it along its normal gives an equivalent termination.

(110)

The plane crosses x and y equally and remains parallel to z. It passes through both corner and body-centred sites, producing BCC's most closely packed surface.

Bulk lattice
Body-centred cubic
Plane normal
[110]
What remains
Rectangular 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 BCC(110) with numbered adsorption sites
The outlined reference cell has |a1| = 4.0588 Å, |a2| = 2.8700 Å, and γ = 90.00° for the Fe slab used in the drawing. Fractional coordinates mean r∥ = ua1 + va2.
  1. ontop1-fold

    Above an atom in a dense surface row.

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

    Projection of the L1 atom at (1/2, 0).

    ASE keywordontop
  2. short bridge2-fold

    Between the closest pair along the compact direction.

    (u,v) = (1/4, 1/4)s = (s₁ + s₂) / 2 · support shell: mean Δz = +0.000 Å from L1

    Periodic midpoint of L1 (1/2, 0) and L1 (0, 1/2).

    ASE keywordshortbridge
  3. long bridge2-fold

    Between atoms across the rectangular channel.

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

    Periodic midpoint of L1 (1/2, 0) and L1 (1/2, 1).

    ASE keywordlongbridge
  4. hollow4-fold

    In the asymmetric opening between rows.

    (u,v) = (5/8, 1/2)exact ASE affine transform · support shell: mean Δz = +0.000 Å from L1

    ASE bcc110 hollow (3/8, 1/4), transformed from its primitive oblique cell into this rectangular cell.

    ASE keywordhollow

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

Atoms in the first two layers interlock to form the dense row pattern; a single-layer view makes the net look more open than it is.

Side profile of BCC(110) showing its first repeating atomic layers
Side profile showing one compact stacking repeat. The dashed line follows the macroscopic surface plane.
Layer registry of BCC(110)
Layer registry viewed from above; opacity increases towards the surface.

Cell

Geometry at a glance

The spacing is \(d_{110}=a/\sqrt{2}\). The outlined conventional rectangle spans \(a\sqrt{2}\) by \(a\) and contains the inequivalent short and long bridge directions.

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 bcc110

slab = bcc110("Fe", size=(3, 4, 6), a=2.87, vacuum=10)
Things that are easy to misread
  • Calling BCC(100), rather than BCC(110), the close-packed BCC face.
  • Treating short and long bridges as equivalent.