Open SC · Parallel ridges

SC(210)

SC(210) tilts the square (100) net into a regular sequence of exposed ridges and lower rows. Its compact repeat is a useful first high-index simple-cubic example.

Plane: (210)
Layer character: Stepped · open
ASE slab builder: surface

From bulk to facet

How SC(210) is cut

(210) plane cutting through a Simple cubic bulk unit cell — The coloured sheet is one translated member of the (210) plane family; translating it along its normal gives an equivalent termination.

(210)

The [210] normal tilts away from [100] towards [110], so the cut crosses successive cubic rows at two different lateral positions.

Bulk lattice: Simple cubic
Plane normal: [210]
What remains: Parallel ridges

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(210) with numbered adsorption sites — The outlined reference cell has |a₁| = 7.4908 Å, |a₂| = 3.3500 Å, and γ = 90.00° for the Po slab used in the drawing. Fractional coordinates mean r_∥ = ua₁ + va₂.

ridge ontop1-fold
Above an atom in the highest exposed row.
(u,v) = (2/5, 0)s = s₁ · support shell: mean Δz = +0.000 Å from L1
Projection of the L1 atom at (2/5, 0).
Not named in ASE
lower-row ontop1-fold
Above an exposed atom in the next lower row.
(u,v) = (4/5, 0)s = s₁ · support shell: mean Δz = -1.498 Å from L1
Projection of the L2 atom at (4/5, 0).
Not named in ASE
ridge bridge2-fold
Between adjacent atoms along the upper ridge.
(u,v) = (2/5, 1/2)s = (s₁ + s₂) / 2 · support shell: mean Δz = +0.000 Å from L1
Periodic midpoint of L1 (2/5, 0) and L1 (2/5, -1).
Not named in ASE
ridge-to-trough bridge2-fold
Between an upper-row atom and its nearest lower-row neighbour.
(u,v) = (3/5, 0)s = (s₁ + s₂) / 2 · support shell: mean Δz = -0.749 Å from L1
Periodic midpoint of L1 (2/5, 0) and L2 (4/5, 0).
Not named in ASE
mixed-height pocket3-fold
A three-atom opening supported by consecutive exposed heights.
(u,v) = (7/15, 1/3)s = (Σᵢ sᵢ) / 3 · support shell: mean Δz = -1.498 Å from L1
Least-squares centroid of the 3-atom projected shell: L1 (2/5, 1), L2 (4/5, 0), L3 (1/5, 0).
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

Each visible row belongs to a different atom-bearing height; the open pocket therefore draws support from more than one layer.

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

For the cubic lattice, \(d_{210}=a/\sqrt{5}\), and the in-plane repeat combines one [001] translation with a longer vector across the steps.

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, (2, 1, 0), 10, vacuum=10)

Things that are easy to misread

Flattening all ridge and trough atoms into one layer in the top view.
Inferring energetic stability from the geometric site labels.