[CP2K:5586] DX in vibrational analysis

[Ali KACHMAR]

Dear Tobias

you will get what you want if you:

1) follow exactly the Juerg's suggestion regarding the scf convergence as
well as for the geometry optimization.

2) make sure for the Vibrational analysis calculations you start from the
optimized geometry (RESTART+GEO_opt)

3)  use DX=0.02

Best regards,
Ali Kachmar

On Wed, Aug 6, 2014 at 3:22 PM, <hut... at chem.uzh.ch> wrote:

> Hi
>
> maybe it would be a good idea to test your settings with a
> smaller molecule.
>
> It looks to me like you should considerably tighten the
> convergence criteria, both for the SCF and the geometry
> optimization. Especially, if you use a small DX you will need
> a very well converged energy.
>
> I would use a RMS_FORCE of 5. 10-5 or smaller and a
> SCF convergence of 1. 10-7 or better.
>
> regards
>
> Juerg Hutter
>
> --------------------------------------------------------------
> Juerg Hutter                         Phone : ++41 44 635 4491
> Institut für Chemie C                FAX   : ++41 44 635 6838
> Universität Zürich                   E-mail: hut... at chem.uzh.ch
> Winterthurerstrasse 190
> CH-8057 Zürich, Switzerland
> ---------------------------------------------------------------
>
> -----cp... at googlegroups.com wrote: -----
> To: cp... at googlegroups.com
> From: Tobias Kraemer <161brun... at gmail.com>
> Sent by: cp... at googlegroups.com
> Date: 08/05/2014 04:11PM
> Subject: [CP2K:5585] DX in vibrational analysis
>
> Dear all,
>
>
> following my previous post (huge number of imaginary frequencies...) on
> this issue, I have in the meantime
> tried to break down to problem into a smaller one.Basically, instead of
> using the full bulk system, I have tried
> a simple optimization and frequency calculation on one of the cationic
> portions (organometallic complex) of the
> system. I have used a cubic cell with a = 20 Ang. I have made sure that
> the structure for the subsequent vibrational
> analysis job does indeed correspond to the final structure of the
> optimization run (I have included ATOMIC_COORDINATES ON
> to print out the geometry in the output).  Again, in the first attempt
> (using DX 0.001) I end up with a huge number (~50) of imaginary
> frequencies, including some very large ones.
>
>  VIB|                        NORMAL MODES - CARTESIAN DISPLACEMENTS
>  VIB|
>  VIB|                         1                    2                    3
>  VIB|Frequency (cm^-1) -4133.188102         -2206.847291
> -2036.718924
>  VIB|Intensities           0.326216             0.395802
> 0.125908
>  VIB|Red.Masses (a.u.)     1.746454             1.699628
> 1.961778
>  VIB|Frc consts (a.u.)    -1.304878            -0.103208
> -0.086426
>
>
> Now, if I repeat the same calculation with a larger DX of 0.01, I end up
> with less imaginary modes, but still too many (17) to trust the result.
> Also, massive change now in the magnitude of the wavenumbers, which drops
> to -957 cm-1 for imaginary mode nr 1. Think the details here
> are not so relevant, but I am quite confused. So the problem is not
> related to the bulk system, but intrinsically related to the vibrational
> analysis protocol I am following at the moment. Also, as far as the SCF is
> concerned, I am using inner / outer SCF  in combination with DIIS.
> Apparently the very first SCF never converges after 100 steps, which is
> when the outer SCF kicks in and from there everything seems to converge
> smoothly. Maybe my thinking is wrong here? This is what it looks like (in
> condensed form) from one of the replica outputs:
>
> rhdcpenba_mol_vib-r-9.out:  *** SCF run NOT converged ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    15 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in     4 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in     6 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in     6 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in     8 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in     9 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in     8 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in     9 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in     9 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    10 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    10 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    13 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    13 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    14 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    15 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    16 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    15 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    15 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    15 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    15 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    15 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    14 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    14 steps ***
> rhdcpenba_mol_vib-r-9.out:  *** SCF run converged in    15 steps ***
>
> So my question really is, how do I choose an appropiate value for DX (and
> other parameters), and what is potentially going wrong here. I am
> absolutely clueless I must say, since I considered this as an 'easy' task.
> I feel that I am just simply doing something wrong, although I thought I
> was following standard procedure. I am keeping all other values such as SCF
> convergence and so on untouched, in order to not introduce any
> inconsistencies here. Would a more rigorous optimisation perhaps be helpful?
>
>
> Thanks for your help, much appreciated. Files attached.
>
> Best
>
> Tobi
>
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>
> [attachment "rhdcpenba_vib0001.out" removed by Jürg Hutter/at/UZH]
> [attachment "rhdcpenba_vib0001.inp" removed by Jürg Hutter/at/UZH]
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