have larger $t_{lm}$ with a two-dimensional character, while the M$\sigma$ band is 1D; therefore, the former show wider bands. The orbital occupancies are {$\bar{n}_{\textrm{M}\sigma}$, $\bar{n}_{\textrm{L}}$} = {0.86, 1.15}, which are substantially varied from the cases above. These features are close to the situation in the MO scheme in Fig. \[fig1\]: In Cu(tmdt)$_2$, the M$\sigma$ ($pd\sigma$) orbital is occupied with nearly one electron.

![image](fig4_rev2.eps){width="14cm"}

\[fig4\]

Let us comment on the relation between our level scheme and the nominal charges given as Ni$^{2+}$\[(tmdt)$^-$\]$_2$, Au$^{3+}$\[(tmdt)$^{1.5-}$\]$_2$, and Cu$^{2+}$\[(tmdt)$^-$\]$_2$. Their corresponding occupations of metal $d$ levels are Ni:(3$d$)$^8$, Au:(5$d$)$^8$, and Cu:(3$d$)$^9$, respectively. When one hypothesizes that the M$\sigma$ and M$\pi$ levels are ‘$d$’ levels of the metal atoms and the L orbitals for the full charge of the ligands (namely, omit $p$-$d$ mixing, which is actually large), these nominal charges correspond to, (M$\pi$)$^2$\[(L)$^1$\]$_2$, (M$\pi$)$^2$\[(L)$^{1.5}$\]$_2$, and (M$\pi$)$^2$(M$\sigma$)$^1$\[(L)$^1$\]$_2$, respectively, namely, a full-filled M$\pi$ in all compounds, and, (i) in $M$ = Ni, a 1/2-filled L band, (ii) in $M$ = Au, a 3/4-filled L band, and (iii) in $M$ = Cu, a 1/2-filled M$\sigma$ band and a 1/2-filled L band. These are close to the situations in Fig. \[fig4\].

Mean-Field Calculation {#sec3}
======================

As mentioned in § 