Summary: Why does G94W's SCF option make errors?

From: "Yubo Fan" <yubofan -x- at -x- guomai.sh.cn>
Subject: Summary: Why does G94W's SCF option make errors?
Date: Wed, 9 Jul 1997 03:18:47 -0000
 Hi,
 I got many help from the CCL. Every advice is important for me, and some of
 them cannot be read from books or Jounals. Thank you very much. Here's the
 summary.
  Hi, ccl'ers,
  I calculated a molecule with 3 Phenyls. I use BLYP/3-21G**. This time, I
  try "restart", a SCF option that I didn't use before. I kill the job
 after
  L502.exe had been running 4 cycles, then I put "restart" after
 "SCF=". I
  ran the calculation again. L502.exe did 2 cycles and the result was
 gotten.
  Again I did the job from the very original start. After 6 cycles had been
  done, another result was gotten. I list them below:
  :With SCF=(save, restart)
  Convergence on energy, delta-E=1.12D-05
   SCF Done:  E(RB-LYP) =  -692.644057005     A.U. after    2 cycles
               Convg  =    0.2054D-03             -V/T =  2.0090
               S**2   =   0.0000
   KE= 6.864357999909D+02 PE=-3.864671343753D+03 EE= 1.355127785196D+03
  :With SCF=save
  SCF Done:  E(RB-LYP) =  -692.644408415     A.U. after    6 cycles
               Convg  =    0.4070D-05             -V/T =  2.0094
               S**2   =   0.0000
   KE= 6.861718246427D+02 PE=-3.864945652472D+03 EE= 1.355665717853D+03
  Why do they have error I think it considerable great?
  Thanks a lot
  Y. FAN
 ===================================================
 FAN, Yubo
 Department of Chemistry
 Fudan University
 Shanghai, 200433
 P. R. China		Voice(86-21)65492222-4294
 ===================================================
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 Re your message about BLYP/3-21G**, in case you didn't get an answer yet :
 Here, you did a Single-Point calculation, I presume. The Cut-Offs for these
 calcs are quite loose, thus the _small_ difference in energy (.027 mH, .04
 kcal/mol). Start it from yet a different position, you'll get a third, also
 diff. number. This problem is I think more significant with DFT than with
 HF.
 If you want 7-8 significant digits, use the option scf(nosp) or scf(tight)
 when you do single points.
 Nest of luck
 Jeremy
 1. This is not a SCF calculation, it is at BLYP (DFT) level.
 2. Are you sure that molecular geometryies are identical?
 =================================================================
 Dr. Buyong Ma             buyong -x- at -x- ibmnla.chem.uga.edu
 Computational Center for Molecular Structure and Design
 Department of Chemistry
 University of Georgia
 Athens, Georgia 30602 USA            Voice (706) 542-2044
 =================================================================
 On Tue, 24 Jun 1997, ~{76S}~}#~{( ~}wrote:
 >
 > Hi, ccl'ers,
 >
 >
 > I calculated a molecule with 3 Phenyls. I use BLYP/3-21G**. This time, I
 > try "restart", a SCF option that I didn't use before. I kill the
 job
 after
 > L502.exe had been running 4 cycles, then I put "restart" after
 "SCF=". I
 > ran the calculation again. L502.exe did 2 cycles and the result was
 gotten.
 > Again I did the job from the very original start. After 6 cycles had been
 > done, another result was gotten. I list them below:
 >
 > :With SCF=(save, restart)
 > Convergence on energy, delta-E=1.12D-05
 >  SCF Done:  E(RB-LYP) =  -692.644057005     A.U. after    2 cycles
 >              Convg  =    0.2054D-03             -V/T =  2.0090
 >              S**2   =   0.0000
 >  KE= 6.864357999909D+02 PE=-3.864671343753D+03 EE= 1.355127785196D+03
 >
 > :With SCF=save
 > SCF Done:  E(RB-LYP) =  -692.644408415     A.U. after    6 cycles
 >              Convg  =    0.4070D-05             -V/T =  2.0094
 >              S**2   =   0.0000
 >  KE= 6.861718246427D+02 PE=-3.864945652472D+03 EE= 1.355665717853D+03
 >
 >
 > Why do they have error I think it considerable great?
 >
 >
 > Thanks a lot
 >
 > Y. FAN
 >
 >
 >
 >
 >
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 > ---
 >
 >
    Dr. Fan,
   If you look at the convergence of the two cases you see that they
 agree to the convergence criteria of the restarted job.  Based on the
 information you supplied it is not clear why G94W would have stopped at
 this point as the RMS change in the density, the value listed as Convg,
 is larger than the default criteria.  If you ran these with #P you can
 look at the status at each iteration and perhaps we can get a clue.
   Also include the information about what revision of G94W you are running.
 > Hi, ccl'ers,
 >
 >
 > I calculated a molecule with 3 Phenyls. I use BLYP/3-21G**. This time, I
 > try "restart", a SCF option that I didn't use before. I kill the
 job
 after
 > L502.exe had been running 4 cycles, then I put "restart" after
 "SCF=". I
 > ran the calculation again. L502.exe did 2 cycles and the result was
 gotten.
 > Again I did the job from the very original start. After 6 cycles had been
 > done, another result was gotten. I list them below:
 >
 > :With SCF=(save, restart)
 > Convergence on energy, delta-E=1.12D-05
 >  SCF Done:  E(RB-LYP) =  -692.644057005     A.U. after    2 cycles
 >              Convg  =    0.2054D-03             -V/T =  2.0090
 >              S**2   =   0.0000
 >  KE= 6.864357999909D+02 PE=-3.864671343753D+03 EE= 1.355127785196D+03
 >
 > :With SCF=save
 > SCF Done:  E(RB-LYP) =  -692.644408415     A.U. after    6 cycles
 >              Convg  =    0.4070D-05             -V/T =  2.0094
 >              S**2   =   0.0000
 >  KE= 6.861718246427D+02 PE=-3.864945652472D+03 EE= 1.355665717853D+03
 >
 >
 > Why do they have error I think it considerable great?
 >
 >
 > Thanks a lot
 >
 > Y. FAN
 >
 >
 >
 >
 >
 > ---
 > Administrivia: This message is automatically appended by the mail
 exploder:
 > CHEMISTRY -x- at -x- www.ccl.net: Everybody | CHEMISTRY-REQUEST -x- at -x-
 www.ccl.net:
 Coordinator
 > MAILSERV -x- at -x- www.ccl.net: HELP CHEMISTRY or HELP SEARCH | Gopher:
 www.ccl.net
 73
 > Anon. ftp: www.ccl.net   | CHEMISTRY-SEARCH -x- at -x- www.ccl.net --
 archive search
 >              Web: http://www.ccl.net/chemistry.html
 > ---
 >
   Douglas J. Fox
   Director of Technical Support
   help -x- at -x- gaussian.com
    Dr. Fan,
    There was a condition with Rev. B.3 where G94W could incorrectly decide
 that the SCF had converged because the energy increased.  This has been
 corrected and may be the cause of your problem.
    While the SCF=Restart option can save you time you must continue to
 check the result to make sure it is reasonable, as you must with any
 computational procedure.
 > Dr. Fox,
 >
 >
 > The Calculation  Package I use is Gaussian 94 Revision-B.3.
 >
 > I will do a big job later, so I must do a test for occasional poweroff or
 > system crack. I kill the job after 4 cycles have done, then I retake the
 > job with option restart.
 >
 > Thanks for your help.
 >
 > Y. FAN
 >
   Douglas J. Fox
   Director of Technical Support
   help -x- at -x- gaussian.com