DFTB problems with mio-1-1 parameter set

[terra...@gmail.com]

HI, all
I was recently running DFTB calculation on a water box containing one acetic acid molecule. I have used the cp2k provided .spl files and everything works fine. Now I want to try the mio-1-1 parameter set from dftb.org, simulations work normally when i use mio-1-1 with DFTB-SCC for a box of water molecules, but once I have the acetic acid molecules in the simulation box, cp2k crash with "chelosky failure". when checking the trajectory of the crashed simulations, I found that the C-H bonds shrink and hydrogens basically collapse into the C atom; the same happens to the carbonyl group (C=O), the oxygen collapse into the C atom. only the hydroxyl group behaves normally. Such problems also exist when just simulated one acetic acid molecule. Attached is my input file for the one acid molecule MD calculation as a test, which crashes after 25 steps. Can anyone having experience using mio-1-1 parameters in cp2k kindly help me on this. Thanks in advance.

Best Regards
Jiasen Guo

[hut...@chem.uzh.ch]

Hi

this is a problem of CP2K not being able to parse all options
of the somewhat cryptic skf file format.

The easy solution here is to change in all X-Y.skf files with
X/=Y the second line from

20*1.0

to

20*0.0

The problem is that this line is used as an indicator if a
spline version of the repulsive potential is available.

hope this solves the problem

regards

Juerg
--------------------------------------------------------------
Juerg Hutter Phone : ++41 44 635 4491
Institut für Chemie C FAX : ++41 44 635 6838
Universität Zürich E-mail: hut...@chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

-----cp...@googlegroups.com wrote: -----
To: "cp2k" <cp...@googlegroups.com>
From: terra...@gmail.com
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Date: 08/15/2018 09:27PM
Subject: [CP2K:10629] DFTB problems with mio-1-1 parameter set

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[attachment "12.26.inp" removed by Jürg Hutter/at/UZH]

[terra...@gmail.com]

Hi
Thanks very much for your help. It does fix the problem! What about the X-Y.skf file when X=Y, e.g. in file O-O.skf, the fourth line reads 20*1.0 also, do we keep it as it is?
BTW, it will be great if someone can redirect me to some materials that explains the format of dftb parameter files.

Best Regards
Jiasen Guo

[hut...@chem.uzh.ch]

Hi

the X-X.skf files have a second line describing the atomic parameters
and the repulsive part and is correctly parsed by CP2K. Replacing this
line by non-zeros for X-Y.skf cases causes the problem.

tou can find all the information on the DFTB website, e.g.

https://www.dftb.org/parameters/introduction/

regards

Juerg
--------------------------------------------------------------
Juerg Hutter Phone : ++41 44 635 4491
Institut für Chemie C FAX : ++41 44 635 6838
Universität Zürich E-mail: hut...@chem.uzh.ch
Winterthurerstrasse 190
CH-8057 Zürich, Switzerland
---------------------------------------------------------------

-----cp...@googlegroups.com wrote: -----
To: "cp2k" <cp...@googlegroups.com>
From: terra...@gmail.com
Sent by: cp...@googlegroups.com

Date: 08/16/2018 06:13PM
Subject: [CP2K:10641] Re: DFTB problems with mio-1-1 parameter set