CCL:G: AW: G09: CASSCF warning

 Sent to CCL by: "Georg Lefkidis" [lefkidis||physik.uni-kl.de]
 Dear Vera,
 although I do not have all the information from your com file, I suspect
 degeneracy (or quasi) here. This means that Gaussian is trying to lower the
 energy and in every iteration there is a level crossing leading to
 convergence-oscillations (in other words every iteration tries to lower the
 energy of a different molecular orbital confusing Gaussian). The way to
 avoid that is to identify the levels that cause the problem and have CASSCF
 minimize the energy for both (or all) of them *at the same time*. Use the
 StateAverage option do to so.
 I hope this helps (it has for me in the past!)
 Best regards
 George
 -----Ursprüngliche Nachricht-----
 Von: owner-chemistry+lefkidis==physik.uni-kl.de.],[.ccl.net
 [mailto:owner-chemistry+lefkidis==physik.uni-kl.de.],[.ccl.net] Im Auftrag
 von
 Vera Cathrine vera.cathrine a yahoo.com
 Gesendet: Mittwoch, 18. Januar 2012 11:39
 An: Lefkidis, Georg
 Betreff: CCL: G09: CASSCF warning
 Sent to CCL by: "Vera  Cathrine" [vera.cathrine^_^yahoo.com] Dear All,
 I am running a CASSCF calculations. G09 issues a warning regarding the large
 rotation of orbitals as shown in the following. I already know that this
 warning signify that the orbitals are not good starting orbitals which
 indicates that there could be problems. However if this occurs only at the
 first steps of the wave-function optimization and the energy converges
 smoothly it seems that this warning is not fatal. However, I dont know how
 these warnings can help me to find the correct orbitals or how to fix the
 warning at all?
 Any general guide is greatly appreciated.
 Best regards,
 Vera
 WARNING! : large rotation  I  J  =                       48
                        38
  Step scaled by    9.8286815811546094E-002
  ITN=  1 MaxIt= 64 E=   -637.5621751557 DE=-6.38D+02 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       49
                        48
  Step scaled by    0.1039006628670738
  ITN=  2 MaxIt= 64 E=   -637.5029804099 DE= 5.92D-02 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       49
                        35
  Step scaled by    0.1427849527680300
  ITN=  3 MaxIt= 64 E=   -637.4932393622 DE= 9.74D-03 Acc= 1.00D-08 Lan=  0
  ITN=  4 MaxIt= 64 E=   -637.4865343884 DE= 6.70D-03 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       49
                        48
  Step scaled by    0.7380582824594381
  ITN=  5 MaxIt= 64 E=   -637.4176733760 DE= 6.89D-02 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       48
                        35
  Step scaled by    0.2877574555342823
  ITN=  6 MaxIt= 64 E=   -637.3770255363 DE= 4.06D-02 Acc= 1.00D-08 Lan=  0
  ITN=  7 MaxIt= 64 E=   -637.3086594950 DE= 6.84D-02 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       53
                        50
  Step scaled by    0.4846317462914080
  ITN=  8 MaxIt= 64 E=   -637.3137340085 DE=-5.07D-03 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       53
                        50
  Step scaled by    0.5107805781250911
  ITN=  9 MaxIt= 64 E=   -637.2887888967 DE= 2.49D-02 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       48
                        23
  Step scaled by    0.3154420167117161
  ITN= 10 MaxIt= 64 E=   -637.2275618744 DE= 6.12D-02 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       48
                        23
  Step scaled by    0.8747886194178708
  ITN= 11 MaxIt= 64 E=   -637.2166647016 DE= 1.09D-02 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       54
                        50
  Step scaled by    0.8117438649098225
  ITN= 12 MaxIt= 64 E=   -637.2032627261 DE= 1.34D-02 Acc= 1.00D-08 Lan=  0
  WARNING! : large rotation  I  J  =                       54
                        50
  Step scaled by    4.5686553052688081E-002
  ITN= 13 MaxIt= 64 E=   -637.1542499631 DE= 4.90D-02 Acc= 1.00D-08 Lan=  0http://www.ccl.net/cgi-bin/ccl/send_ccl_messagehttp-:-//www.ccl.net/chemistry/sub_unsub.shtmlhttp-:-//www.ccl.net/spammers.txt