Open FCC · Narrow terraces
FCC(210)
Tilting away from (100) towards (110) produces the open (210) surface. Its short terraces repeat rapidly, creating pronounced ledges and low-coordinate ridge atoms.
- Plane
- (210)
- Layer character
- Stepped · very open
- ASE slab builder
surface
From bulk to facet
How FCC(210) is cut
(210)
Relative to (100), the [210] normal is tilted towards [110]. The resulting atomic cut resolves into a rapidly repeating staircase of short terraces.
- Bulk lattice
- Face-centred cubic
- Plane normal
- [210]
- What remains
- Narrow terraces
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
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.
- ridge ontop1-fold
Above a low-coordinate atom on the upper ridge.
(u,v) = (1/5, 1/2)s = s₁ · support shell: mean Δz = +0.000 Å from L1Projection of the L1 atom at (1/5, 1/2).
Not named in ASE - lower-row ontop1-fold
Above an exposed atom in the row below the ridge.
(u,v) = (2/5, 0)s = s₁ · support shell: mean Δz = -0.807 Å from L1Projection of the L2 atom at (2/5, 0).
Not named in ASE - ridge bridge2-fold
Between neighbouring atoms along the upper ridge.
(u,v) = (1/5, 0)s = (s₁ + s₂) / 2 · support shell: mean Δz = +0.000 Å from L1Periodic midpoint of L1 (1/5, 1/2) and L1 (1/5, 3/2).
Not named in ASE - ridge-to-lower bridge2-fold
Between atoms on the ridge and lower row.
(u,v) = (13/20, 1/4)s = (s₁ + s₂) / 2 · support shell: mean Δz = -0.807 Å from L1Periodic midpoint of L1 (7/10, 0) and L3 (3/5, 1/2).
Not named in ASE - trough pocket4-fold
In the mixed-height pocket within the open trough.
(u,v) = (11/20, 1/2)s = (Σᵢ sᵢ) / 4 · support shell: mean Δz = -0.404 Å from L1Least-squares centroid of the 4-atom projected shell: L1 (7/10, 0), L1 (7/10, 1), L2 (2/5, 0), L2 (2/5, 1).
Not named in ASE
Interactive model
Rotate the slab
Sites share a schematic display height · drag to rotate · hover for names
Below the top layer
Why the sites are different
The profile makes the terrace-and-step interpretation explicit: the surface normal averages over a staircase of atomic ledges rather than passing through a single flat layer.
Cell
Geometry at a glance
The normal is \([210]\), \(d_{210}=a/\sqrt{5}\), and its angle from [100] is \(\cos^{-1}(2/\sqrt{5})\approx26.6^\circ\).
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
cu = bulk("Cu", "fcc", a=3.61, cubic=True)
slab = surface(cu, (2, 1, 0), layers=8, vacuum=10)
Things that are easy to misread
- Treating all visible rows as equally high; the side profile shows their step sequence.
- Assigning a low-index ASE site keyword to a high-index surface without checking coordinates.