Invalid lattice parameters vs reported symmetry

Materials Project
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1

The material mp-22730 (Na2MoO4) is reported with Fddd (#70) space group but the conventional lattice parameters do not match

Lattice (Conventional)
a 6.35 Å
b 12.64 Å
c 6.04 Å
α 90.00 º
β 121.65 º
ɣ 90.00 º
Volume 412.76 ų

Search on other database make me think that this might a report error as ICSD report indeed this structure but with the parameters

Cell parameter 6.4499(7) 12.783(1) 10.856(1) 90. 90. 90. Space group F d d d Z (70)
Cell volume 895.07 [ų]

where a and b are identical but c is not

ICSD source:

Author Bramnik, K.G.; Ehrenberg, H.; Title Study of the (Na2 O) - (Mo O3) system. Na6 Mo11 O36 - a new oxide with anatase-related structure and the crystal structures of Na2 Mo O4
Reference Zeitschrift fuer Anorganische und Allgemeine Chemie (1950) (DE) (2004) 630, p. 1336-1341 (4 structures) DOI 10.1002/zaac.200400119

I didn’t find another place to report this kind of errors (at least in material project FAQ)

2

Hey @leonard-IMBERT this is a case where automatic symmetry determination is very sensitive to the tolerances used. Changing the linear distance tolerance used to identify the space group changes it drastically:

from mp_api.client import MPRester

s = MPRester().get_structure_by_material_id("mp-22730")
for symprec in (0.01, 0.1):
    print(symprec,s.get_space_group_info(symprec=symprec))
>>> 0.01 ('C2/c', 15)
>>> 0.1 ('Fddd', 70)

Also keep in mind that the MP structure can be any repeat unit of the primitive cell. If we transform the structure to its conventional representation, the symmetry is more apparent:

conv = s.to_conventional(symprec=0.1)
print(conv.lattice.abc)
print(conv.lattice.angles)
>>> (6.349580320450959, 10.286833706850889, 12.638767248826353)
>>> (90.0, 90.0, 90.0)