CCL:G: CASSCF Memory Requirements



Dear Soren Eustis,
Reading the error message, I think you have not provided sufficient memory required by the job. The job required at least 33GB of RAM memory. So, specified it by %mem=33GB. If you do not have sufficient physical memory, you should lower the level of computation either by reducing the number of basis functions or by freezing more orbitals in CASSCF procedure.

Best regards,

On 31 December 2010 10:11, Soren Eustis soren]~[env.ethz.ch <owner-chemistry_+_ccl.net> wrote:

Sent to CCL by: "Soren  Eustis" [soren+*+env.ethz.ch]
Greetings.  I am trying to do a CASSCF(6,6) conical optimization of a medium sized molecule.  Using the 6-31++G basis set, I end up with 350 basis functions.  This is y first foray into CASSCF on Gaussian, and I feel that I must be making an error because the job always halts with a not enough memory error.  I have tried increasing up to 8gb per processor (!) running 4 processors.  This cannot be correct!  I was being frugal by choosing a (6,6) active space, yet I am still running out of resources.  I was unable to find a good discussion of casscf memory issues, so I am posting my question here. I would greatly appreciate some help with this.  Abridged input and output below.

Regards,

Soren Eustis
ETH - Zurich

*************************************
 Gaussian 09:  AM64L-G09RevA.02 11-Jun-2009
               31-Dec-2010
 ******************************************
 %chk=CASSCFConical.chk
 %mem=32GB
 %nprocshared=8
 Will use up to    8 processors via shared memory.
 Default route:  MaxDisk=2GB
 ----------------------------------------------------------------------
 # opt(conical) casscf(6,6,slaterdet,nroot=2)/6-31++g scrf=(iefpcm,solv
 ent=water) guess=save pop=savenlmo geom=connectivity


****

electronic state of the initial guess is 1-A.
 Out-of-memory error in routine OMatEl (IEnd=    4294966401 MxCore=    4294966296)
 Use %mem=4097MW to provide the minimum amount of memory required to complete this step.
 Error termination via Lnk1e in /cluster/apps/gaussian/g09/l405.exe at Fri Dec 31 06:07:36 2010.
 Job cpu time:  0 days  0 hours  0 minutes 19.1 seconds.
 File lengths (MBytes):  RWF=     89 Int=      0 D2E=      0 Chk=      1 Scr=      1



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J. Jules.