Gaussian 92 disk requirements for UMP2 frequencies
Subject: Disk space requirements for an MP2 G92 freq job
Hello,
I am trying to complete a MP2 full core, open shell, analytic
frequency calculation with 188 basis functions (306 uncontracted
ones) of a 10 atom system( 2 C, 1 O, and 7 H) with no symmetry
using the Gaussian92 application. Unfortunately, the formula that
predicts the disk space requirements of such a job (3*N^4/4 words
of disk space, page 92, line 12 from the top of the Gaussian92
User's Guide when used with the keywords "verystingy" and
"scf=direct") does not seem completely accurate, at least for the
Cray X/MP. On a smaller job (130 basis functions) the ammount
needed seemed closer to 4*N^4/5 words.
Using the formula I find I need 7,495,190,016 bytes. I ran the
job on a 8.2 gigabyte partition and the job failed after
completing the MP2 gradient part because it run out of disk space
(while writing on the *.scr file).
Gaussian 92 revisions A and B take more disk for UMP2 frequencies than
the documented amounts. The good news is that revision C, which is
now shipping and which has been sent to your site automatically
because you are on maintenance, has been greatly improved in this area,
and now takes more like 1/2 N^4 words. The procedure for these big
jobs should be to use MP2=(Stingy,MaxDisk=N) SCF=Direct, where N is
the disk limit for the queue (or a bit less for safety). VeryStingy
will be done automatically if necessary. There is still a fixed
minimum amount of disk, but this will do the best it can. For RevC
and the job above this should be under 7 GBytes, so if you run in your
8 GByte queue and specify MaxDisk=950000000 things should work fine.
Mike Frisch
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