GeMg2: enthalpy of formation
4 accepted literature formation-enthalpy value(s) (experimental 3, model 1); experimental median -38.409 kJ/mol-atom (n = 1); Materials Project -25.946 kJ/mol-atom (mp-aaaaaaps); OQMD -26.833 kJ/mol-atom (oqmd-646873).
Systems: Ge–Mg
Literature values
| Value | Phase as printed | T (K) | Class | Method | System | Source | Location | Quote |
|---|---|---|---|---|---|---|---|---|
| -115.37 unspecified ± 0.25 | Mg2Ge | 298.15 | experimental | Ge–Mg | [1] Islam 2006 cites Beardmore 1966 | p. 5 report | They found that the heat of formation of Mg2 Ge at 298 K from the solid elements is -104.23 ± 1.26 kJ, whereas Beardmore et al. [30] reported the same as -115.37 ± 0.25 kJ, showing a disagreement between the two values. | |
| -104.23 unspecified ± 1.26 | Mg2Ge | 298.15 | experimental | EMF | Ge–Mg | [1] Islam 2006 | p. 5 report | They found that the heat of formation of Mg2 Ge at 298 K from the solid elements is -104.23 ± 1.26 kJ, whereas Beardmore et al. [30] reported the same as -115.37 ± 0.25 kJ, showing a disagreement between the two values. |
| -38.409 kJ/mol-atom ± 0.0837 | Mg2Ge | 273 | experimental | Solution calorimetry | Ge–Mg | [1] Islam 2006 cites Bever 1964 | Table 3, p. 5, row 4 report | |
| -39.3728 kJ/mol-atom | Mg2Ge | 298.15 | model | Thermodynamic modeling | Ge–Mg | [1] Islam 2006 | Table 3, p. 5, row 6 report |
Uncertainty budget
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.
| Value | Unit | Printed | Reading | Method (class, basis) | Composition | Scatter | Conversion | Effective |
|---|---|---|---|---|---|---|---|---|
| -115.37 | unspecified | 0.25 | 0.005 | unit 'unspecified' not convertible to kJ/mol-atom | 0.25 | |||
| -104.23 | unspecified | 1.26 | 0.005 | unit 'unspecified' not convertible to kJ/mol-atom | 1.26 | |||
| -38.409 | kJ/mol-atom | 0.0837 | 5.000e-5 | 3.2 (solution_reaction_calorimetry, calibrated) | 3.2 | |||
| -39.3728 | kJ/mol-atom | 5.000e-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.
| Source | Entry | kJ/mol-atom | eV/atom | Space group | E above hull (kJ/mol-atom) | E above hull (eV/atom) | Theoretical |
|---|---|---|---|---|---|---|---|
| Materials Project | mp-aaaaaaps | -25.946 | -0.268911 | Fm-3m | 0 | 0 | no |
| OQMD | oqmd-646873 | -26.833 | -0.278103 | Fm-3m | 0 | 0 | no |
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
- F. Islam, A.K. Thykadavil, M. Medraj, A computational thermodynamic model of the Mg–Al–Ge system, Journal of Alloys and Compounds 425, 129-139 (2006). doi:10.1016/j.jallcom.2006.01.050