Sent to CCL
by: Tobias Kraemer [tobiask##chem.gla.ac.uk]
Dear CCLs
I came accross
a result obtained with Gaussian03 that I can't explain. In order to investigate
the dependence on HF exchange, I optimised a copper complex I'm interested
in,
using the "user-defined DFT model" keywords as described in the manual
(setting IOps 3/76 to 3/78 with BLYP keyword). Apart from different values for
the HF exchange parameter,
the parameters for the remaining exchange and
correlation functionals were kept constant (B3LYP values were
used).
Comparing the result for the user defined functional (20% HF)
calculation, with the result for the same calculation but using the B3LYP
keyword, the former yields
exactly the same optimisation steps with same
energies, and exactly the same final geometry and energy. However, the same
calculation gives 6 negative frequencies (-197i, 196i, 195i, 127i, 93i, 29i
cm-1) for this structure.
In the 'pure' B3LYP optimisation the same structure
corresponds to a true minimum. How can the frequencies be so different although
the calculations are in fact the same (this is actually the example from the
manual).
Am I missing something here??
Here are my input files (the
defined .chk-files are the same in both cases, so the initial conditions are the
same)
For user-defined
model:
%NProc=4
%mem=6000MB
%chk=cu2_N_no2tmemach_BLYP_hf-20.chk
#P
UBLYP/gen IOp(3/76=1000002000) IOp(3/77=0720008000) IOp(3/78=0810010000) opt
freq gfprint gfinput pop=full guess=read geom=check
HF=20%
1
2
Cu N O
0
6-311+G(2df)
**************
C H
0
6-31G*
**************
For
B3LYP
keyword
%NProc=4
%mem=6000MB
%chk=cu2_N_no2tmemach_B3LYP.chk
#P
UB3LYP/gen opt freq gfprint gfinput pop=full geom=check
HF=20% with
B3LYP
1 2
Cu N O
0
6-311+G(2df)
**************
C H
0
6-31G*
**************
Any
ideas will be very much appreciated. Thanks.
Tobias
--
____________________________________
dipl.-chem. tobias kraemer
westCHEM, department of chemistry
university of glasgow
joseph black
building
university avenue
glasgow G12 8QQ
scotland, uk
|phone|
+44 (0)141 330 8121
|email|
tobiask%x%chem.gla.ac.uk
____________________________________
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