# gaussian problems

• Organization: Imperial College, London
• Subject: gaussian problems
• Date: Tue, 09 Jul 2002 14:13:41 +0100

```Dear all,
I have two question and one information concerning gaussian.
1)
I wanted to perform an optimization with possibly slowest  changing
of geometry. The command line was as:
#P OPT=(Redundant,CalcAll,StepSize=1,TIGHT) INT=(GRID=99590)
I got an error:
QPERR --- A SYNTAX ERROR WAS DETECTED IN THE INPUT LINE.
#P OPT=(REDUNDANT,CALCALL,STEPSIZE=1,TIG
'
What's wrong? On p.129 of User's reference one can find description
of StepSize in Opt and I can't see why it shouldn't work.
2)
However calculation of IR was already sometimes discussed on CCL I
still have uneasy feeling. An example.
I have a molecule with trigonal bipiramide (D3h) structure. I know
however that minimum is distorted - both axial ligands are moved out
of Z-axis in direction of one equatorial ligand (f.e.: ax-ax angle 160)
and the equatorial are still co-planar (C2v).
(I hope that you can imagin it from my description).
Now: If I would distorte D3h structure to C2v with ax-ax angle 175 deg
and optimized geometry with frozen ax-ax, should IR calculation have
a one imaginary freq. narrowing ax-ax angle or not? If it gives me no
Imag - hwat does it mean?
One can find in books that vibrational analysis should be performed
only on stationary point - if not it's meaningless. What sense has it
if one makes such restriction? If I want to be sure that I'm in minimum
should I repaet all symmetry bounded calculation (like above D3h)
with NoSymm?
3)
Last week I wanted to calculated some quite complicated
molecules like CO or CCH2 and various level of theory.
Everything was fine with DFT and MP2 but the same inputs
didn't work for CCSD and CCSD(T).
The input like:
%MEM=1000MB
%NPROC=2
%SAVE
%CHK=CO-CCSD
carbon monoxid
0 1
C         0.000000000000      0.000000000000      0.000000000000
O         0.000000000000      0.000000000000      1.126962524921
produced an error:
Symbolic Z-matrix:
Charge =  0 Multiplicity = 1
C                     0.        0.        0.
O                     0.        0.        1.12696
Leave Link  101 at Fri Jul  5 17:23:43 2002, MaxMem=   13107200 cpu:       0.2
(Enter /usr/local/SW/g98/l114.exe)
NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-NEF-
NUMERICAL EIGENVECTOR FOLLOWING MINIMUM SEARCH
INITIALIZATION PASS
************************************************
** ERROR IN INITNF. NUMBER OF VARIABLES (  0) **
**   INCORRECT (SHOULD BE BETWEEN 1 AND 50)   **
************************************************
Error termination via Lnk1e in /usr/local/SW/g98/l114.exe.
I was supprised that gaussian was looking for z-matrix even if I wrote
opt=cart.  I've repeated the calculation with opt=z-matrix and geometry:
C
O    1   r1
r1  =  1.126962524921
and gaussian succeed with Normal Termination. So probably I've found small
bug.
Thanks a lot in advance and best reagrds
Krzysztof
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