Dear All： Thank you ,David Shobe! The 6-311++G** is the only basis I tried with diffuse functions. So I think this is the most important point. Now I test aug-cc-pVTZ, and also got a quite good result. Ding Xunlei 2003-04-11 ______________________________________________ Ding Xunlei, Ph.D. Candidate Open Laboratory of Bond Selective Chemistry University of Science & Technology of China Hefei, Anhui 230026, P.R.China Tel.: 0086-551-3603418 Fax.: 0086-551-3602969 E-mail: dxl "at@at" mail.ustc.edu.cn Http://www.bsc.ustc.edu.cn/~dxl ____________________________________________________________________________________________ My next question: Is 6-311++G** the only basis you tried with diffuse functions (usually indicated by a '+' in the name)? These are usually necessary for any calculation involving anions. You might also want to check for spin contamination. --David Shobe
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