RbF2
RbF2 is a metastable, semiconducting fluoride compound that serves as a subject of fundamental research into non-standard chemical structures.
About RbF2
Rubidium difluoride is a metastable inorganic compound that exhibits semiconducting electronic behavior. Its existence as a fluoride phase highlights the complex coordination chemistry possible within the rubidium-fluorine system, where stoichiometry deviates from the more common stable configurations.
Because it is a metastable material, it is of significant interest to researchers studying phase transitions and high-pressure synthesis techniques. Its structural diversity, evidenced by numerous reported configurations, makes it a subject of fundamental study in solid-state chemistry.
Key Properties
Cross-validated computational properties for RbF2, aggregated across 3 databases.
Band GapEnergy needed to move an electron from the valence band to the conduction band. Lower or zero values tend to behave more metallic; larger gaps are more insulating or semiconducting.
Energy Above HullThermodynamic distance from the most stable set of competing phases. 0 eV/atom is on the convex hull; small positive values may still be experimentally accessible.
StabilityA plain-language summary of the best reported energy-above-hull result. It reflects whether the lowest-energy structure is on, near, or far from the stability hull.
StructuresCount of reported calculated crystal structures for this formula, including alternate polymorphs, source databases, and observed space groups.
Cross-Source DFT Agreement
How well independent DFT databases agree on the thermodynamics of RbF2. Tight agreement means computed properties can be trusted without re-running calculations.
Agreement ScoreA normalized confidence score summarizing how closely independent DFT databases agree. Higher scores mean tighter cross-source agreement.
Hull SpreadDifference between the highest and lowest energy-above-hull values reported by comparable sources. Smaller spread means less thermodynamic disagreement.
Sources ComparedNumber and names of computational sources with comparable entries for this formula.
Space Group ConsensusWhether independent sources predict the same crystal symmetry for the lowest-energy structure.
Reported Structures
Lowest-energy structures reported for RbF2, ranked by energy above hull.
| Space GroupSymmetry classification of the crystal arrangement. The number is the international space-group index. | Crystal SystemBroad lattice family, such as cubic, tetragonal, monoclinic, or triclinic, derived from unit-cell symmetry. | Band Gap (eV)Electronic gap calculated for this specific reported structure, measured in electronvolts. | E above hull (eV/atom)Thermodynamic distance from the convex hull for this structure, normalized per atom. Lower is generally more stable. | E/atom (eV)Computed total energy normalized per atom. Use energy above hull, not this value alone, when comparing stability. | Density (g/cm³)Mass per relaxed crystal volume, reported in grams per cubic centimeter. |
|---|---|---|---|---|---|
| P42/mnm (No. 136) | tetragonal | 1.43 | 0.0516 | -3.718 | 2.94 |
| P42/mnm (No. 136) | tetragonal | 1.35 | 0.1147 | -1.927 | — |
| — | — | 0.00 | 0.1625 | -1.925 | — |
| P42/mnm (No. 136) | tetragonal | 0.00 | 0.2124 | -1.829 | — |
| — | — | 8.62 | 0.3196 | -1.768 | — |
| — | — | 0.00 | 0.4244 | -1.663 | — |
| C2 (No. 5) | monoclinic | — | — | — | 2.03 |
| P1 (No. 1) | triclinic | — | — | — | 1.93 |
| P-1 (No. 2) | triclinic | — | — | — | 1.46 |
| P-1 (No. 2) | triclinic | — | — | — | 3.03 |
| P-1 (No. 2) | triclinic | — | — | — | 2.86 |
| P-1 (No. 2) | triclinic | — | — | — | 2.40 |
Frequently Asked Questions
Common questions about RbF2, answered from cross-validated data.
What is RbF2?
RbF2 is a metastable, semiconducting fluoride compound that serves as a subject of fundamental research into non-standard chemical structures.
What is the band gap of RbF2?
Is RbF2 a metal, semiconductor, or insulator?
Is RbF2 thermodynamically stable?
What is the crystal structure of RbF2?
What is the density of RbF2?
How many polymorphs of RbF2 are known?
What elements does RbF2 contain?
Where does the data for RbF2 come from?
How It Compares
As an unclassified and metastable phase, RbF2 represents a specialized case within fluoride materials, where typical stability rules are challenged. Unlike conventional ionic fluorides that favor highly stable, fixed oxidation states, this compound occupies a unique niche that demands precise synthesis conditions to maintain its structural integrity.
Data sources & attribution
- materials_project — Data from the Materials Project (materialsproject.org). Cite: Jain et al., APL Materials 1, 011002 (2013). (CC-BY-4.0)
- jarvis — Data from JARVIS (jarvis.nist.gov), NIST. Cite: Choudhary et al., npj Comp. Mater. 6, 173 (2020). (LicenseRef-US-Gov-PD)
- oqmd — Data from the OQMD (oqmd.org). Cite: Saal et al., JOM 65, 1501 (2013); Kirklin et al., npj Comp. Mater. 1, 15010 (2015). (CC-BY-4.0)
- mpaloe — Data from MP-ALOE. Cite: Kuner et al., npj Comput. Mater. (2025), doi:10.1038/s41524-025-01834-9.
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