KCN
Potassium cyanide · Cyanide of potassium
Potassium cyanide is a highly reactive inorganic salt that functions as a potent chemical reagent in industrial and laboratory settings.
About Potassium cyanide
Potassium cyanide is a crystalline inorganic compound characterized by its insulating electronic nature. It is widely recognized for its high reactivity and role in various specialized chemical synthesis pathways. Due to its position above the thermodynamic hull, the compound is considered inherently unstable under standard conditions. Its structural versatility is evidenced by the numerous distinct crystalline arrangements reported across scientific databases.
Key Properties
Cross-validated computational properties for Potassium cyanide, 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 KCN. 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 KCN, 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. |
|---|---|---|---|---|---|
| Imm2 (No. 44) | orthorhombic | 5.44 | 0.1087 | -0.406 | — |
| Cc (No. 9) | monoclinic | 5.16 | 0.1091 | -0.406 | — |
| R3m (No. 160) | trigonal | 4.97 | 0.1244 | -0.391 | — |
| Cc (No. 9) | monoclinic | 5.06 | 0.1256 | -8.752 | 1.54 |
| P1 (No. 1) | triclinic | 5.14 | 0.1260 | -8.751 | 1.51 |
| — | — | 5.09 | 0.1290 | -0.338 | — |
| — | — | 5.18 | 0.1309 | -0.336 | — |
| Imm2 (No. 44) | orthorhombic | 5.31 | 0.1392 | -8.738 | 1.61 |
| Cm (No. 8) | monoclinic | 5.04 | 0.1691 | -8.708 | 1.75 |
| — | — | 5.03 | 0.1761 | -0.291 | — |
| P1 (No. 1) | triclinic | 1.23 | 0.7537 | -8.124 | 2.14 |
| Cm (No. 8) | monoclinic | 0.06 | 0.9691 | -7.908 | 2.40 |
Applications
Where Potassium cyanide is used.
Frequently Asked Questions
Common questions about Potassium cyanide, answered from cross-validated data.
What is KCN?
Potassium cyanide is a highly reactive inorganic salt that functions as a potent chemical reagent in industrial and laboratory settings.
What is KCN used for?
What is the band gap of KCN?
Is KCN a metal, semiconductor, or insulator?
Is KCN thermodynamically stable?
What is the crystal structure of KCN?
How many polymorphs of KCN are known?
What elements does KCN contain?
Where does the data for KCN come from?
How It Compares
As a standalone compound in this context, potassium cyanide serves as a primary example of a cyanide-based salt that exhibits significant structural polymorphism despite its thermodynamic instability.
Data sources & attribution
- jarvis — Data from JARVIS (jarvis.nist.gov), NIST. Cite: Choudhary et al., npj Comp. Mater. 6, 173 (2020). (LicenseRef-US-Gov-PD)
- materials_project — Data from the Materials Project (materialsproject.org). Cite: Jain et al., APL Materials 1, 011002 (2013). (CC-BY-4.0)
- 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.
- cod — Data from the Crystallography Open Database (crystallography.net/cod/). Cite: Grazulis et al., J. Appl. Cryst. 42, 726 (2009). (CC0-1.0)
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