CCL:G: about electron affinity
- From: "Pierre Archirel"
- Subject: CCL:G: about electron affinity
- Date: Tue, 2 Sep 2014 12:15:04 -0400
Sent to CCL by: "Pierre Archirel" [pierre.archirel~~u-psud.fr]
I have a closed shell molecule (rather large: 12 first row atoms) and I want to
know if this molecule can bind an electron.
DFT tells me "yes" with positive values of the electron affinity, in
the range 0.5-1.0 eV according to the functional. I suspect that these values
are false, or at least largely overestimated.
I now turn to ab initio methods, but I first see that at the HF level the
electron is not bound and the SOMO built of the most diffuse gaussians of the
The CCSD(T) and SAC-CI methods (which are affordable in my case) give a negative
electron affinity... but are these methods reliable? These methods use the HF
orbitals, can they bind an electron if it is not bound at the HF level?
Or shall I use CAS methods (very expansive in my case) which optimize orbitals
at the CI level? Is it obligatory in this case?
Many thanks in advance,
LCP, Universite Paris-Sud, Orsay, France