CCL: Optimization with B3lyp functional in DFT

From: "Senthil kumar Krishnasamy" <supersenthil73/./gmail.com>
Subject: CCL: Optimization with B3lyp functional in DFT
Date: Tue, 27 Mar 2012 21:48:02 -0400

 Sent to CCL by: "Senthil kumar  Krishnasamy"
 [supersenthil73^gmail.com]
 Dear all
 I had optimized the structures of Trifluoromethane sulfonyl fluride [CF3SO2F]
 and trifluromethane sulfonic acid [CF3SO2OH]   with Hartree fock method with
 equilibrium bond lengths and bond angles between the atoms. But the same
 compounds are optimized with B3lyp functional; I get a deviation from
 equilibrium bond length between carbon and sulphur atoms, sulphur and fluorine
 atoms of 0.02 , 0.05 , and 0.08 respectively. I used the Keywords of
 int=ultrafine, geom. =conn, opt=vtight with B3lyp functional. I didnt get the
 equilibrium bond lengths for the above case.  The oxidation state of sulphur
 atom is followed by a value of 6 for both the compounds. I done the freq
 calculation for the same compounds by HF method and there is no imaginary
 frequency. What is the key word to be used to get the equilibrium bond length
 between carbon & sulphur atoms and sulphur & fluorine atoms in the
 optimization step using B3lyp functional?
 I expect the possible help from all.
 Thanks in advance
 By
 K. Senthil kumar
 Faculty of Physics
 HIndusthan College of engg & tech
 Coimbatore-32