There are many ways to calculated electronic spectra.
CIS is a very cheap, reasonable wavefunction methodology.
You can also use TD-DFT (someone stated that range-separated functionals are better; this is not true for excited states, as the ground and excited states will have the same error and it will be subtracted off very commonly). As DFT is is often heavily parameterized, it will fail in some cases, but not others. Hence, sometimes people encourage comparing to experiment (although this somewhat defeats the point).
The best methods are EOM-CCSD or MR-CI excited state calculations, depending on if dynamic or static correlation is expected to be the greater issue. These methods have the advantage is that they do not require any notion of comparing to experiment; they have no parameters, and are thus equally likely to do well on any system (aside the issue of static vs. dynamic correlation) because they are based on systematically moving to the exact wavefunction answer.
Given that you are doing benzene, a highly symmetric molecule with few atoms, you could easily afford to do EOM-CCSD or MR-CI if you wish to.
Remember to use diffuse functions in your basis set, always, to describe excited states.
On 8/19/15 10:45 PM, Hao-Bo Guo guohaobo{:}gmail.com wrote:
Try TDDFT. Several functionals may do an excellent job for benzene, especially the range-separated functionals CAM-B3LYP, wB97XD, LC-wPBE. Others such as doubly hybrid B2PLYPD, and meta-GGA hybrid M06-2X, may also do a good job for benzene. The basis set you used may be too small, but acceptable. Your really need an assessment for the functionals, basis set etc, using the experimental spectra as the reference.
----From my experience in TDDFT calculations of the benzoic acid derivatives (JPCA 2012). Hao-Bo Guo
On Wed, Aug 19, 2015 at 5:11 PM, Kaci Tiziouzou kaci.tiziouzou/./gmail.com <owner-chemistry()ccl.net> wrote:
Hi all,
Can anyone share with me the procedure that I can use to get a UV-VIS spectrum for Benzene. I am currently using the TD-SCF in gaussian 09 with a 6-31G basis set (Hartree Fock) and my value is way below the experimental.
I must be doing something wrong!!
Thanks in advance
K.T
-- Dr. Robert Molt Jr. r.molt.chemical.physics/a\gmail.com Nigel Richards Research Group Department of Chemistry & Chemical Biology Indiana University-Purdue University Indianapolis LD 326 402 N. Blackford St. Indianapolis, IN 46202