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 ( R₁, R₂-DCNQI)₂M with M0ex0ex=0ex0exCu 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, R₁, and R₂, and the essential features of the observed Fermi surfaces of (DMe-DCNQI)₂Cu with R₁0ex0ex=0ex0exR₂0ex0ex=0ex0exCH₃ 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.