Components kept separate, in the value's unit (literature SCHEMA.md, UNCERTAINTY_CALIBRATION.md): effective = max(sqrt(max(printed, reading, method)^2 + composition^2 + conversion^2), scatter). The method floor is the robust between-study scatter of the method class in ORCHID (calibrated) or a documented prior; printed values and printed uncertainties are unchanged.
Uncertainty budget of the literature values of Fe3O4
Value
Unit
Printed
Reading
Method (class, basis)
Composition
Scatter
Conversion
Effective
-159.411
kJ/mol-atom
7.143e-5
3.9 (model_calculated, calibrated)
3.9
DFT formation energies
Lowest-energy entries at this composition. Materials Project and OQMD use different energy references and are never averaged. 1 eV/atom = 96.485 kJ/mol-atom.
DFT formation energy of Fe3O4
Source
Entry
kJ/mol-atom
eV/atom
Space group
E above hull (kJ/mol-atom)
E above hull (eV/atom)
Theoretical
Materials Project
mp-aaaabcoo
-157.23
-1.62958
Fd-3m
1.26
0.0131
no
OQMD
oqmd-1362615
-160.234
-1.66071
I41/amd
0
0
yes
DFT sources: A. Jain et al., Commentary: The Materials Project: A materials genome approach to accelerating materials innovation, APL Materials 1 (2013) 011002. doi:10.1063/1.4812323 (CC BY 4.0); J. E. Saal et al., JOM 65 (2013) 1501-1509; S. Kirklin et al., npj Comput. Mater. 1 (2015) 15010. doi:10.1007/s11837-013-0755-4 (CC BY 4.0);
Sources
B Sundman, An assessment of the Fe-O system, JPE 12, 127-140 (1991). doi:10.1007/bf02645709