Potassium intercalated graphyne

Graphyne intercalation compounds are expected to function as layered organic conductors and as storage of atoms and molecules, because graphyne as a host material is highly stable and has large voids. We have performed optimization of the geometry and calculation of the electronic structures for five hypothetical stacking arrangements of the stage-1 potassium-intercalated graphyne by use of the first-principles method. The results are compared with the values of the typical graphite-intercalation compound, C8K. The stability of potassium-intercalated graphyne is strongly dependent on the position of intercalated atoms relative to the characteristic voids in the pristine graphyne. It is found that some stacking arrangements are stable, and are expected to intercalate potassium easily since the estimated values of the heat of reaction are larger than that of C8K. For the optimized crystal structures the electronic structures show that these materials are metallic. Further, we show the relationship between the amount of charge transfer and each bond length in graphyne.