Low-index FCC · Rectangular rows

FCC(110)

The (110) cut is the most open low-index FCC face. Close-packed atomic rows run in one direction, separated by troughs that make the two in-plane axes visibly inequivalent.

Plane: (110)
Layer character: Flat · strongly anisotropic
ASE slab builder: fcc110

From bulk to facet

How FCC(110) is cut

(110) plane cutting through a Face-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 meets two cubic axes equally and remains parallel to the third. Its diagonal passage through the cube produces dense rows separated by open channels.

Bulk lattice: Face-centred cubic
Plane normal: [110]
What remains: Rectangular rows

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 FCC(110) with numbered adsorption sites — The outlined reference cell has |a₁| = 5.1053 Å, |a₂| = 3.6100 Å, and γ = 90.00° for the Cu slab used in the drawing. Fractional coordinates mean r_∥ = ua₁ + va₂.

ontop1-fold
Directly above an atom on a close-packed row.
(u,v) = (1/4, 1/2)s = s₁ · support shell: mean Δz = +0.000 Å from L1
Projection of the L1 atom at (1/4, 1/2).
ASE keywordontop
short bridge2-fold
Between nearest neighbours along a row.
(u,v) = (1/2, 1/2)s = (s₁ + s₂) / 2 · support shell: mean Δz = +0.000 Å from L1
Periodic midpoint of L1 (1/4, 1/2) and L1 (3/4, 1/2).
ASE keywordshortbridge
long bridge2-fold
Between atoms across neighbouring rows.
(u,v) = (1/4, 0)s = (s₁ + s₂) / 2 · support shell: mean Δz = +0.000 Å from L1
Periodic midpoint of L1 (1/4, -1/2) and L1 (1/4, 1/2).
ASE keywordlongbridge
trough hollow4-fold
In the channel between the raised rows.
(u,v) = (1/2, 0)s = (Σᵢ sᵢ) / 4 · support shell: mean Δz = +0.000 Å from L1
Least-squares centroid of the 4-atom projected shell: L1 (1/4, -1/2), L1 (3/4, -1/2), L1 (1/4, 1/2), L1 (3/4, 1/2).
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

The side profile reveals ridges and troughs even though the macroscopic plane is flat. Atoms below the trough change the coordination of sites that appear empty from above.

Side profile showing one compact stacking repeat. The dashed line follows the macroscopic surface plane.

Layer registry viewed from above; opacity increases towards the surface.

Cell

Geometry at a glance

The cubic plane spacing is \(d_{110}=a/\sqrt{2}\). The outlined conventional surface cell spans \(a\sqrt{2}\) along a doubled close-packed-row repeat and \(a\) across the rows.

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 add_adsorbate, fcc110

slab = fcc110("Cu", size=(3, 3, 4), a=3.61, vacuum=10)
add_adsorbate(slab, "H", 1.2, position="hollow")

Things that are easy to misread

Using “bridge” without specifying whether it runs along or across a row.
Treating the rectangular net as isotropic.