Ir basis sets (w/ ECPs)
We just published a paper in JACS (1st issue of the year, ca.
page 340, sorry I'm out of town and don't have the ref.) in which we
looked at methane activation by Ir complexes using the ECPs and attendent
valence basis sets of Walt Stevens and co. Indeed, Walt et al. have
developed a consistent ECP/valence basis set scheme up to Rn (I noticed
someone was interested in Ba a few days ago). We have used the transition
metal ECPs and valence basis sets extensively and find that in the overwhelming
majority of cases, if you're using the right type wwavefunction (RHF, GVB,
etc.) you're gonna get good results.
To be fair, the Los Alamos people have developed ECPs for Ir,
although off the top of my head I can't recall an application. Same
thing applies to the ECPs developed by Pitzer et al.
The Stevens ECP/basis set scheme is quadruple zeta for the
s and p manifolds; triple zeta for the d manifolds. I believe
Frenking et al. have optimized f exponents for the entire transition
series if you want to add polarization. I believe this was in a
recent Chem Phys Letter.
Hope this is of some help.