Structural and electronic properties of ${\mathrm{K}}_{\mathit{n}}$${\mathrm{C}}_{60}$

We present local-density pseudopotential calculations of the structural and electronic properties of potassium fulleride ${\mathrm{K}}_{\mathit{n}}$${\mathrm{C}}_{60}$ (n=1,2,3,6) crystals, with an emphasis on the superconducting ${\mathrm{K}}_3$${\mathrm{C}}_{60}$ phase. The calculated enthalpies of reaction for all of the potassium fullerides are within 1.4–1.7 eV per K atom. The pressure-versus-volume equation of state indicates that ${\mathrm{K}}_3$${\mathrm{C}}_{60}$ is less compressible than ${\mathrm{C}}_{60}$. The band structure ${\mathrm{K}}_3$${\mathrm{C}}_{60}$ is very similar to that of ${\mathrm{C}}_{60}$, and we discuss how it changes with pressure. Using calculated valence charge densities, we show that the valence electrons of the K atoms are almost completely transferred to the lowest unoccupied bands of the ${\mathrm{C}}_{60}$ molecular solid.