[molpro-user] VSCF calculation

Fabian Berger bergerfa at hu-berlin.de
Wed Feb 7 10:28:29 CET 2018

```Dear molpro user,
I have calculated the attached VSCF calculation. This calculations
finished properly but the results are quite suspicious.
Please have a look at the frequencies (which are printed after the full
VSCF calculation) below:

Mode    Harmonic    Diagonal      VSCF      E(abs)
21     3895.46    35100.93    94654.42   *********
20     2287.49    11388.67     9714.29   *********
19     2263.76     2242.11     3415.39   *********
18     1952.70     2036.93     2797.70   *********
17     1930.40     8892.65    13269.76   *********
16     1041.72      582.15      257.85   *********
15      990.83      620.67     1839.88   *********
14      937.69      747.23     1553.29   *********
13      894.56       88.28    12701.39   *********
...

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:

Mode     Harmonic     Diagonal     Intens
21 A       3895.46      3726.10     167.28
20 A       2287.49      2214.86     149.16
19 A       2263.76      2191.54     158.09
18 A       1952.70      1895.77     246.07
17 A       1930.40      1874.12     287.72
16 A       1041.72      1035.21     342.11
15 A        990.83       985.04     122.05
14 A        937.69       949.79      39.75
13 A        894.56       933.24     426.63
...

I have the following questions:

1) What is the difference between the 1D frequencies after calculating
the 1D potentials and the full PES calculation?
2) Why do such non-senseful frequencies arise after the calculation of
the coupling terms in the 1D frequencies?
3) Which input parameters could I adjust to fix this problem?

Thank you very much!

Best regards,
Fabian Berger

Input file:

***,anharm
memory,960,m
file,1,surfdebug.int
file,2,surfdebug.wf
angstrom
geometry={
O,     1.37395990000000,    3.12849230000000,    -2.72838240000000
Al,     0.11308370000000,    1.80597310000000,    -3.67800270000000
O,     -1.01719110000000,    2.68772110000000,    -2.58192110000000
Si,     0.01089600000000,    3.62802360000000,    -1.76857130000000
H,     2.24328820000000,    2.96029440000000,    -2.35571480000000
H,     0.59049360000000,    0.37640650000000,    -3.19723810000000
H,     0.05245040000000,    2.19748800000000,    -5.20403290000000
H,     -0.17319630000000,    5.08032320000000,    -1.91244630000000
H,     0.29860050000000,    3.28203280000000,    -0.36344240000000
}

! structure relaxation
basis,default=cc-pvtz
{hf
accu,14}
ccsd(t)
optg

! hessian
mass,iso
frequencies,symm=no

! PES calculation
label1
int
{hf
start,atden
accu,14}
ccsd(t)
goto,label3

label2
{df-rks,pbe0;disp}
goto,label3

label3
{surf,start1D=label1,sym=no,ndim=2,ngrid=8,plot=2
vmult,start2D=label2,Multi=1
disk,save=5600.2,where=home,dump='surfdebug.pot'}

! VSCF
poly,dipole=0
vscf,type=poly,thermo=1,dipole=0
```