Subject: summary: g92/dft-rwf-files

From: [email-masked] (Christoph Ehrendorfer)
Date: Tue, 24 Jan 1995 15:40:53 +0100 (MET)

Dear CCL-members,

Since I got several requests for summaries on my question concerning
g92-rwf-files, here it is. I am sorry that the summary comes so late, but
first I did not want to make a summary at all, since no REAL solution is
offered for my problem.

Here is my original question:

> I have a question concerning the case of large RWF-files in Gaussian
> 92/DFT. Doing analytical
> FREQ calculations the RWF-file grows to remarkable size and sometimes
> becomes larger than the available diskspace (or the limit of
> the file-system specified by the operating system).
> 
> Im am working on a AIX-system and I am thinking about the possibility to
> split the RWF-file in two files and to put them on two different
> file-systems. So my question is, if this splitting of the RWF-file is
> possible (and HOW) ?
> 
> But I would also be happy to get other comments on the possibility to
> decrease the amount of necessary diskspace during analytical FREQ
> calculations.

These are the answers, facts (as i understood them) and rumours:

i) It is not possible to split rwf-files using g92/dft.

ii) It might be possible that in  a future release there will be some option
for rwf-file splitting. 

iii) Using numerical calculation of the second derivative will decrease the
need for resources. 

iv) There are systems (CRAY, DEC  ........) where the file
system size is larger than on AIX 3.2 systems. But with the
AIX 4.x there might also be a higher limit.

v) Usage of SCF=DIRECT reduces disk space. 

And here are my thoughts about these things:

ad iii) Since I am working on rather large systems with low symmetry, this
option would increase the cpu-time very strong.

ad v) I think the 2-e-integrals
are stored NOT in the rwf, but in the d2e-file. Thus, this option would
reduce the need for disk space, but not reduce the size of the rwf-file.

Thanks to all who responded and to all who showed interest in my problem

Christoph Ehrendorfer
Institut fuer Theoretische Chemie
Waehringerstrasse 17
1090 Wien

Tel.: +43 1 40480 / 676
FAX:  +43 1 402 85 25