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<font size="-1">Dear Fabian,<br>
<br>
your calculation may have failed for different reasons:<br>
<br>
a) A calculation with ngrid=8 usually does not provide meaningful
results. ngrid is NOT the number of ab initio points in one
dimension, but the number of fine grid points, which is used in
subsequent calculations for the wave function. ngrid controls also
(to some extent) the maximum elongations along the normal
coordinates. As ngrid=8 is far too low, this will lead to very
small surfaces. Note that the default is ngrid=16. Once your
surfaces are too small, the effective potentials within the VSCF
calculations may not be high enough in the outer regions to harbor
the VSCF wave function.<br>
<br>
b) It is very disturbing that your 1D vibrational frequencies
within the SURF program show meaningful results, while the
diagonal frequencies in the VSCF are completely wrong. Essentially
both calculations should give (more or less) the same answer. The
differences are (1) that the 1D calculations within the SURF
program do not include the Watson correction term, while this term
will be added in the POLY calculation and thus it is included in
the 1D calculation in the VSCF program. However, this effect
should by small and cannot explain the huge differences, which you
can see here. (2) The 1D calculations in the VSCF program are
based on polynomials, while the 1D calculations in the SURF
program just request the grid points and use a DVR procedure for
calculating the energies. Most likely, it is the polynomial fit,
which causes you the trouble in your calculations. Did you check
the chi^2 values in the POLY program? Are they meaningful? How do
the polynomials look like? <br>
<br>
c) You did neither shift nor scale your individual normal
coordinates (SCALNM,AUTO=ON), which might lead to the situation,
that the 1D potential of individual normal coordinates is very
unbalanced. This may be the reason, why the polynomial fit runs
into trouble. Since you have plotted the potentials, you can
easily control this by visual inspection. <br>
<br>
d) What can you do to rescue your existing surface? (1) You may
leave out the polynomial fitting (POLY) and may use the grid based
VSCF program instead. (2) You may transform the potential to a
grid representation with more grid points using the VGRID program.
Then you may use this representation to enter the grid-based VSCF
code. But I am afraid that you need to rerun the calculations with
ngrid=16, the automated scaling a.s.o.<br>
<br>
I hope this helps.<br>
Best wishes,<br>
<br>
Guntram<br>
<br>
<br>
</font><br>
<div class="moz-cite-prefix">On 02/07/18 10:28, Fabian Berger wrote:<br>
</div>
<blockquote cite="mid:21e73d63d70857ae479850282c28b82d@hu-berlin.de"
type="cite">Dear molpro user,
<br>
I have calculated the attached VSCF calculation. This calculations
finished properly but the results are quite suspicious.
<br>
Please have a look at the frequencies (which are printed after the
full VSCF calculation) below:
<br>
<br>
Mode Harmonic Diagonal VSCF E(abs)
<br>
21 3895.46 35100.93 94654.42 *********
<br>
20 2287.49 11388.67 9714.29 *********
<br>
19 2263.76 2242.11 3415.39 *********
<br>
18 1952.70 2036.93 2797.70 *********
<br>
17 1930.40 8892.65 13269.76 *********
<br>
16 1041.72 582.15 257.85 *********
<br>
15 990.83 620.67 1839.88 *********
<br>
14 937.69 747.23 1553.29 *********
<br>
13 894.56 88.28 12701.39 *********
<br>
...
<br>
<br>
While the harmonic frequencies appear to be reasonable, the 1D
frequencies (Diagonal) and VSCF frequencies deviate significantly.
Interestingly, the frequencies which are printed during the PES
calculation (after the 1D part) seem to be much more similar to
the harmonic values:
<br>
<br>
Mode Harmonic Diagonal Intens
<br>
21 A 3895.46 3726.10 167.28
<br>
20 A 2287.49 2214.86 149.16
<br>
19 A 2263.76 2191.54 158.09
<br>
18 A 1952.70 1895.77 246.07
<br>
17 A 1930.40 1874.12 287.72
<br>
16 A 1041.72 1035.21 342.11
<br>
15 A 990.83 985.04 122.05
<br>
14 A 937.69 949.79 39.75
<br>
13 A 894.56 933.24 426.63
<br>
...
<br>
<br>
I have the following questions:
<br>
<br>
1) What is the difference between the 1D frequencies after
calculating the 1D potentials and the full PES calculation?
<br>
2) Why do such non-senseful frequencies arise after the
calculation of the coupling terms in the 1D frequencies?
<br>
3) Which input parameters could I adjust to fix this problem?
<br>
<br>
Thank you very much!
<br>
<br>
Best regards,
<br>
Fabian Berger
<br>
<br>
<br>
Input file:
<br>
<br>
***,anharm
<br>
memory,960,m
<br>
file,1,surfdebug.int
<br>
file,2,surfdebug.wf
<br>
angstrom
<br>
geometry={
<br>
O, 1.37395990000000, 3.12849230000000,
-2.72838240000000
<br>
Al, 0.11308370000000, 1.80597310000000,
-3.67800270000000
<br>
O, -1.01719110000000, 2.68772110000000,
-2.58192110000000
<br>
Si, 0.01089600000000, 3.62802360000000,
-1.76857130000000
<br>
H, 2.24328820000000, 2.96029440000000,
-2.35571480000000
<br>
H, 0.59049360000000, 0.37640650000000,
-3.19723810000000
<br>
H, 0.05245040000000, 2.19748800000000,
-5.20403290000000
<br>
H, -0.17319630000000, 5.08032320000000,
-1.91244630000000
<br>
H, 0.29860050000000, 3.28203280000000,
-0.36344240000000
<br>
}
<br>
<br>
! structure relaxation
<br>
basis,default=cc-pvtz
<br>
{hf
<br>
accu,14}
<br>
ccsd(t)
<br>
optg
<br>
<br>
! hessian
<br>
mass,iso
<br>
frequencies,symm=no
<br>
<br>
! PES calculation
<br>
label1
<br>
int
<br>
{hf
<br>
start,atden
<br>
accu,14}
<br>
ccsd(t)
<br>
goto,label3
<br>
<br>
label2
<br>
{df-rks,pbe0;disp}
<br>
goto,label3
<br>
<br>
label3
<br>
{surf,start1D=label1,sym=no,ndim=2,ngrid=8,plot=2
<br>
vmult,start2D=label2,Multi=1
<br>
disk,save=5600.2,where=home,dump='surfdebug.pot'}
<br>
<br>
! VSCF
<br>
poly,dipole=0
<br>
vscf,type=poly,thermo=1,dipole=0
<br>
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<br>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
********************************************************************************
Apl. Prof. Dr. Guntram Rauhut
Institut f. Theoretische Chemie
Universitaet Stuttgart
Pfaffenwaldring 55
D-70569 Stuttgart
Germany
Tel. : +49/(0)711/685-64405
FAX : +49/(0)711/685-64442
E-Mail : <a class="moz-txt-link-abbreviated" href="mailto:rauhut@theochem.uni-stuttgart.de">rauhut@theochem.uni-stuttgart.de</a>
HTTP : <a class="moz-txt-link-abbreviated" href="http://www.uni-stuttgart.de/theochem/rauhut/">www.uni-stuttgart.de/theochem/rauhut/</a>
********************************************************************************
</pre>
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