Subject: G92 mp2 freq calc using little disk

From: <[email-masked]>
Date: Mon, 15 Aug 1994 10:28:25 -0400 (EDT)

>>From:	IN%"[email-masked]" 14-AUG-1994 22:15:28.00
>>To:	IN%"[email-masked]"
>>CC:	
>>Subj:	CCL:G92: Help with MP2 FREQ calc.
>>
>>Running MP2 FREQ calculation on an optimized geometry.
>>156 basis functions.
>>MAXDISK = 100 MW
>>MP2=VERYSTINGY
>>
>>Problem:
>>G92 tries to create a 400MW .rwf (3.2GB!) file and runs out of disk space.
>>I have 2G available for temp files.
>>

Kong, I've had luck using the following:

# mp2/basis freq=Numer SCF=Direct 

Using scf=direct cuts down the disk requirement because atomic ints aren't
stored.  (For 156 basis fuctions, it may also be faster than using an integral
file.)  Using freq=numer cuts down the disk requirement because only first
derivatives are calculated analytically.  Using freq=numer also slows the
calculation considerably, but, unlike the analytic second derivative
calculation, it can be restarted from the checkpoint file using
freq=(numer,restart). 

If this still doesn't work, maybe specifying mp2=fulldirect in addition to
freq=numer will do it.

Good luck! 

Karl 

----------------------------------------------
Dr. Karl Irikura
Chemical Kinetics and Thermodynamics Division
National Institute of Standards and Technology
Gaithersburg, MD  20899
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