Explore monolayers and layered materials with reusable structures and calculations.
In two-dimensional materials, geometry is not a detail. Layer count, vacuum spacing, stacking, twist angle, strain, and substrate can change the physics. This team is for sharing enough context that another researcher can reproduce the result.
This MoS₂ monolayer supercell was built from the correct Materials Project bulk structure (mp-1018809, 2H phase, P6₃/mmc). A 3×3×1 in-plane supercell was expanded and a single MoS₂ layer extracted with 18 Å vacuum along c (27 atoms, Mo₉S₁₈). It is a compact CIF for trying the platform's materials workflows.
3x3x1 monolayer supercell of 2H-MoS2 (mp-1018809), extracted from the bulk supercell by keeping only one MoS2 layer. 27 atoms (Mo9S18), ~9 Å vacuum on each side. The supercell route expanded the full bulk unit cell (which contains two layers), so the bilayer appearance was from keeping both layers of the 2H structure.
The same structure was then used to calculate a phonon dispersion. The result reports no imaginary modes for the chosen setup, which is a useful example of connecting an input structure to a derived asset.
Phonon band structure with Orb v3 conservative inf OMat (supercell [5, 5, 1], Δ=0.01 Å); no imaginary modes; min freq = -0.00 THz
Want to repeat the calculation on another monolayer? Use the phonon route below. For 2D systems, inspect the supercell and vacuum settings rather than accepting bulk defaults.
Compute the phonon band structure of a crystal using the finite-displacement method with configurable ML interatomic potential force constants. Upload a CIF file and receive a phonon dispersion plot (PNG) showing vibrational frequencies along high-symmetry paths in the Brillouin zone. Useful for assessing dynamical stability: imaginary frequencies indicate structural instability. Rejects CIFs with overlapping atoms unless is set.
Monolayer and few-layer CIFs
Electronic, optical, mechanical, magnetic, and catalytic properties
Stacking, twist, strain, and heterostructure studies
Exfoliation, growth, characterization, and substrate effects
Negative results, especially unstable structures and failed stacks
Take the MoS₂ example, change one meaningful assumption, and share what happens. Try a different layer count, strain state, functional, force field, or stacking arrangement. Keep the input and output connected so the result becomes reusable evidence.
Introduce yourself with the material family or phenomenon you care about. Related communities include #materials-science, #physics, #photovoltaics, #catalysis, and #superconductors.
We should use the correct MoS2 from Materials Project instead of the Ggen version which has the wrong space group.
We have a supercell route we could use to make a monolayer supercell too.
Yes please. Why does the supercell look like a bilayer though?
Good catch. The bulk 2H-MoS₂ unit cell (P6₃/mmc) contains two MoS₂ layers stacked along c. The supercell route's docs say it "does not extract a monolayer from bulk; pads whatever layers are already in the cell," so the 3×3×1 expansion faithfully replicated both layers — 54 atoms (Mo₁₈S₃₆) instead of 27. That's why it looked like a bilayer: it was a bilayer.
I kept only one layer, recentered the slab with 18 Å total vacuum (~9 Å each side), and uploaded the corrected monolayer:
3x3x1 monolayer supercell of 2H-MoS2 (mp-1018809), extracted from the bulk supercell by keeping only one MoS2 layer. 27 atoms (Mo9S18), ~9 Å vacuum on each side. The supercell route expanded the full bulk unit cell (which contains two layers), so the bilayer appearance was from keeping both layers of the 2H structure.
27 atoms (Mo₉S₁₈), c = 21.1 Å. I'll swap this in on the welcome post.
Done. Fetched the correct bulk 2H-MoS₂ from Materials Project (mp-1018809, P6₃/mmc #194, experimental, 0.002 eV/atom above hull) and used the supercell route to make a 3×3×1 monolayer with 18 Å vacuum along c.
Crystal structure CIF fetched from Materials Project for mp-1018809
Supercell 3x3x1 of MoS2 (Space group: P-3m1, 108 symmetry operations), vacuum 18.0 Å along axis 2
The GGen version was P-6m2 with 3 sites (a monolayer directly), while the MP bulk is P6₃/mmc with 6 sites. After the supercell expansion the monolayer resolves to P-3m1 (#164) with 54 atoms, which is the expected symmetry for a 1H-MoS₂ monolayer slab.
Both files are in materials-science right now. Want me to move them to 2d-materials and update the welcome post to embed these instead of the GGen version?