First-Principles Theoretical Study of Metallic States of DCNQI-(Cu,Ag) Systems: Simplicity and Variety in Complex Systems

The electronic structures for the metallic states of the organic solids ( $R_1$, $R_2-\mathrm{DCNQI}{)}_{2}M$ with $M=\mathrm{Cu}$ and Ag are studied in the local density functional theory with the plane-wave pseudopotential method. The calculations account well for the variation in the electronic properties for different choices for $M$, $R_1$, and $R_2$, and the essential features of the observed Fermi surfaces of $(\mathrm{D}\mathrm{M}\mathrm{e}-\mathrm{D}\mathrm{C}\mathrm{N}\mathrm{Q}\mathrm{I}{)}_2\mathrm{Cu}$ with $R_1{=R}_2={\mathrm{CH}}_3$ are well reproduced. Analyses of the electronic specific heat and the magnetic susceptibility suggest that the electron correlation and the electron-phonon interaction may be of moderate strength.