Could anybody explain me the meaning of the data point “number of atoms” that is shown for any material on the material project website? I thought that it was supossed to tell the number of atoms per unit cell, but, in many cases, it doesn’t make any sense to me. For instance, TaC (https://next-gen.materialsproject.org/materials/mp-1086: (Cubic, Fm-3m, 225)) exihibits a fcc crystal structure and, thus, should feature 4 atoms per unit cell. However, “number of atoms” on the website says that it’s 8.
What am I missing?
Hello, Seif Eugen.
Mateirals Project counting of atoms is different from we are used to. An FCC lattice, for crystallography, has 1 atom from 8 1/8 of atom in each corner, and for each two faces, 1 atom. So, you correctly summed 4 atoms, but Materials Peoject counts every atom inside the cell as if it was 1, because it's considering a cell without symmetry.
I know it's confusing. Do you need to do this to generate an input for some computational software?
Best regards,
Ricardo Tadeu.
Yes, but that's right. Apparently, this is the number of formula units in the unit cell volume.
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