First-principles prediction on geometrical and electronic properties of K-doped chrysene

The significant discovery of superconductivity in potassium (K) doped polycyclic aromatic hydrocarbons (PAHs) provides a novel system to understand the superconducting mechanism. Here, we focus on K-doped chrysene which is possibly a superconductor. Chrysene contains four benzene rings, however, the superconductivity induced by the K doping has not been discovered. Based on the first-principles calculations with the Van der Waals functional correction, we predicted the geometrical and the electronic structures of Kx -doped chrysene (x=1, 2, 3 and 4). We found that the K doping results in the phase transition from C2/c to P21 symmetry. The result of the formation energies shows that K2-doped chrysene is the most stable and can easily be fabricated. K2chrysene is still a semiconductor, but K2chrysene with small charge fluctuation can behave as a metal and is thermodynamically stable. Our results provide a route to experimentally obtain the stable K-doped chrysene with metallic feature.