Dear Uwe, dear Tomasz and all others who are interested in MP2 geometry optimization!
1) Problems with mp2prep/mpgrad for large cases:
- mpgrad has for a long time not been updated, the code is quite a bit outdated...,
particulary, it can not deal with huge disc space and file sizes available today!
As soon as one of the file sizes/pointers gets close to 16GB mpgrad gets
integer overflows aborts (with messages which indicate completly different problems.)
- mp2prep invokes mpgrad for a stastics run and often does not detect or handle properly
such problems of mpgrad
Here is my way to avoid this problem:
- specify for mp2prep on the command line allways a maximum amount of disc space
of at most 15000 Mb (using the -p option)
- check, if the file sizes written by mp2prep into the control file are all positive and smaller
then 15000 Mb, if not, invoke again mp2prep, but let it start the statistic run(s) with an
increased number of loops (using the -l option)
Well, it's not an optimal work around, but mp2grad is today almost only used as benchmark
for checking the quality of RI-MP2...
2) How to run efficiently RI-MP2 calculations:
a) the recommended way to set up the control file for RI-MP2 calculations is through the
mp2 submenu of define! rimp2prep is no longer needed. All options for RI-MP2
calculations which can be set with rimp2prep can also be set in define.
b) the RI-MP2 code in the
ricc2 program is in almost any case
more efficient than the
(older) code in the
rimp2 program. The input is only slidely different and can also
prepared with the define program. (see Chem. Phys. Lett. 358, 350-353 (2002) at
http://dx.doi.org/10.1016/S0009-2614(02)00609-7).
All the best,
Christof