# CCL:G: Hessian Matrix in Internal Coordinates

*From*: Andrea Coletta <andrea_coletta**libero.it>
*Subject*: CCL:G: Hessian Matrix in Internal Coordinates
*Date*: Sun, 23 Nov 2008 17:33:33 +0100

Sent to CCL by: Andrea Coletta [andrea_coletta,,libero.it]

`Hi, i'm trying to obtain the Hessian Matrix output in Internal
``Coordinates, from a B3LYP Optimization job with Gaussian03.C02.
` My route section is:
#P B3LYP/6-31G* OPT=CalcAll SCRF=CPCM

`if I use this with a small molecule (e.g Water), in the log file I
find
``something like:
` (Enter /apps/GEN03.C02/g03/l103.exe)
GradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGradGrad
Berny optimization.
Internal Forces: Max 0.000010959 RMS 0.000006781
Search for a local minimum.
Step number 4 out of a maximum of 20
All quantities printed in internal units (Hartrees-Bohrs-Radians)
Second derivative matrix not updated -- analytic derivatives used.
Trust test= 1.00D+00 RLast= 3.53D-03 DXMaxT set to 4.24D-01
The second derivative matrix:
R1 R2 A1
R1 0.46509
R2 -0.00302 0.46509
A1 0.02978 0.02978 0.16989
Eigenvalues --- 0.16394 0.46802 0.46812
RFO step: Lambda= 0.00000000D+00.
and this is exactly what I want!
It works also with an HF Opt test-job I did with Glycine:
#P HF/3-21G OPT=(ModRedundant,CalcAll) SCRF=pcm
[...]
Force constants in Cartesian coordinates:
1 2 3 4 5
1 0.809587D+00
2 0.000000D+00 0.790299D+00
3 0.137405D-01 0.000000D+00 0.642144D+00
4 -0.114527D+00 0.000000D+00 -0.475510D-02 0.644272D+00

` 5 0.000000D+00 -0.110951D+00 0.000000D+00 0.000000D+00
``0.621385D+00
`` 6 0.118871D-01 0.000000D+00 -0.243725D+00 -0.379120D-02
``0.000000D+00
` [...]
Force constants in internal coordinates:
1 2 3 4 5
1 0.426378D+00
2 0.122242D-01 0.472234D+00
3 0.115444D-01 0.547739D-02 0.471563D+00
4 0.115444D-01 0.547739D-02 0.574356D-02 0.471563D+00

` 5 0.138575D-01 -0.102523D-02 -0.441368D-02 -0.441368D-02
``0.404944D+00
`` 6 0.737045D-02 0.195704D-03 0.204429D-03 -0.726729D-03
``0.548064D-02
`

`This is very good... the only difference is that it does'nt specify
``the internal coordinate, and it wrote the Matrix just before enthering
``l103.exe... rather than just after entering, like in the Water
``calculation...
`

`When I try with another molecule a little greater (33 Atoms) it
does'nt
``work!!,
``It does'nt print in the log the Hessian matrix, and in the fchk I find
``only the Hessian Matrix in Cartesian coordinates...
`

`I use use the same Route section, and i've tried a lot of other
``combinations but nothing's working!
` #P B3LYP/6-31G* OPT=CalcAll SCRF=CPCM
or
#P B3LYP/6-31G* OPT=(Redundant,CalcAll) SCRF=CPCM
or
#P B3LYP/6-31G* OPT=(ModRedundant,CalcAll) SCRF=CPCM
or
#P B3LYP/6-31G* OPT=CalcFC
etc. etc.

`Maybe the problem is that my system has too many internal degree of
``freedom (96)?
` Any Suggestions?
Please Help me!! :-(
Thanks
*****************************
Andrea Coletta
Post-Grad. Student
University of "Tor Vergata"
Rome - Italy
*****************************