Subject: g94 compound freq+opt

From: "Michael Probst" <[email-masked]>
Date: Thu, 30 Nov 1995 16:53:01 +0000

Dear Gaussian - experts:
The following input:

-----------------------------------------------
 #P BLYP/aug-cc-pVTZ SCF=DIRECT OPT=Z-MATRIX FREQ MAXDISK=13000000

 NITRAT:aug-cc-pVTZ

-1 1
 N1
 O2    1     RONN
 O3    1     RONN      2     AOON
 O4    1     RONN      2     AOON      3     TORS      0
Variables:
 RONN=1.271
Constants:
 AOON=120.
 TORS=180.
------------------------------------

seems to work well but upon cloeser looking there is a large energy 
difference between the energy at the end of the optimization 
(-280.470491943) and the energy calculated in the frequency step 
(-280.446822509). 
I would not expect the NO3- ion to behave that way and further, if I 
make a independent frequency calculation with the optimized N-O 
distance (1.280612 Angstroem) I get the same energy as in the 
optimization job (and, of course, different frequencies as in the 
compound job) 
Can somebody tell me the reason for the differences in the job with 
freq and opt together ?

Thanks a lot !
Michael

---------------------------------------------------------------------------
Michael Probst                          Internet: [email-masked]
Department of Inorganic Chemistry       Fax:      ++43(512)507 2934
Innsbruck University                    Tel:      ++43(512)507 5153
Innrain 52a
Austria