CCL:G: regarding excited state optimization

 Sent to CCL by: Susi Lehtola [susi.lehtola . alumni.helsinki.fi]
 On 03/16/2016 11:19 PM, navjot navu1989mann(_)gmail.com wrote:
 
 Respected sir,
          I am working with vanadium oxide clusters. V4O10 cluster in its
 ground state optimized by using TZVP/B3LYP in gaussian 09 suit of
 program. Now, I want to optimize first excited state of V4O10 cluster. I
 had already tried by using TDSCF and CIS but my job didn"t get converge.
 Further by using this excited state i need to explore the PES for
 reaction of V4O10 +C6H6. Please help to to give proper input for this
 job.. I shall be very thankful for this act of kindness.
I'm betting the reason why you get the convergence problems is that it's a transition metal oxide system. These tend to be extremely tricky due to strong correlation.
Now, you're trying to model it with a single-reference method, which typically have a swath of local solutions for the ground state, and convergence is terribly poor. Also, because of the similarity of CIS to stability analysis, I bet you'd find negative excitation energies in the calculation.
You might have much better luck getting the runs to converge using pure DFT, even just the LDA might be the most accurate functional for these systems... 
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 Mr. Susi Lehtola, PhD             Chemist Postdoctoral Fellow
 susi.lehtola-.-alumni.helsinki.fi   Lawrence Berkeley National Laboratory
 http://www.helsinki.fi/~jzlehtol  USA
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