Can you read the NTE mechanism off the crystal structure? Structural fingerprints (occupancy-weighted Maxwell floppiness f=(3n−m)/3n with ASE covalent radii +0.40 Å cutoff, mean coordination, 2-coordinate linker fraction, packing openness, density) for 9 known negative-thermal-expansion materials spanning 5 mechanisms (rigid-unit modes, transverse linker modes, ferroelectric, magnetovolume, electronic/Mott) and 3 positive-expansion controls (dense ionic, dense metal, floppy framework). Structures from COD (cod_id column) or built from prototypes ('built'); all CIFs passed the structure sanity card v4.4.
| name | cod_id | formula | n_sites | mechanism | atoms_per_a3 | density_g_cm3 |
|---|---|---|---|---|---|---|
| ZrW2O8 | 1000396 | Zr(WO4)2 | 44 | rigid-unit modes | 0.0574 | 5.08 |
| ScF3 | 4127282 | ScF3 | 4 | rigid-unit modes | 0.0619 | 2.62 |
| ReO3 | 1010031 | ReO3 | 4 | rigid-unit modes | 0.0768 | 7.47 |
| Zn(CN)2 | 4119771 | Zn(CN)2 | 10 | transverse linker modes | 0.052 | 2.03 |
| Ag2O | 4318188 | Ag2O | 6 | transverse linker modes | 0.0567 | 7.27 |
| PbTiO3 | 2107521 | TiPbO3 | 5 | ferroelectric (polarization) | 0.0792 | 7.98 |
| Fe65Ni35 (Invar) | built | Fe35Ni19 | 108 | magnetovolume | 0.0861 | 8.13 |
| Mn3GaN | 1009074 | Mn3GaN | 5 | magnetovolume (AFM order) | 0.0844 | 6.97 |
| Ca2RuO4 | 1526044 | Ca2RuO4 | 28 | electronic (Mott/orbital) | 0.0788 | 4.58 |
| MgO | 1000053 | MgO | 8 | control: dense ionic | 0.1067 | 3.57 |
| Ni | built | Ni | 4 | control: dense metal | 0.0914 | 8.91 |
| alpha-quartz | 1011097 | SiO2 | 9 | control: floppy framework | 0.0797 | 2.65 |