[CP2K:9933] Problematic DFTB geometry optimization

[hut... at chem.uzh.ch]

Hi

the problems with the optimization point to either problems with
the skf files or the structure. Unfortunately, I cannot help with
this directly. But I would test energies between DFTB+ and CP2K
to see if CP2K reads the files correctly. CP2K can only process
a subset of the options available in DFTB+. Check for example
if you have the same number of basis functions. You can do also
cross tests with small molecules (TiO2 etc).
The other possibility would be to run MD with annealing. You should
get to a point with small gradient and then you can see if this
also corresponds to a minimum of energy.

best regards

Juerg
--------------------------------------------------------------
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: cp2k <cp... at googlegroups.com>
From: Maxime Van den Bossche 
Sent by: cp... at googlegroups.com
Date: 01/30/2018 12:14AM
Subject: [CP2K:9933] Problematic DFTB geometry optimization

Hello!

I've been trying out the DFTB module in CP2K on a simple 
bulk TiO2 (rutile) structure. Strangely enough, it appears
impossible for the different optimizers to successfully
relax this structure. With BFGS, the atoms keep oscillating
along some kind of vibrational mode. With CG and LBFGS,
no such oscillations occur, but the forces cannot be brought
below circa 0.015 Hartree/Bohr.

I've attached a zip file with the input and output files for
the different optimizers. I've generated the Slater-Koster files
myself, and they work nicely with the DFTB+ code (without 
any geometry optimization issues). I'm using a development 
version of CP2K (6.0, git:8b033c3).

Could you help me understand what is going on? 

Best,
Maxime




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[attachment "files.zip" removed by Jürg Hutter/at/UZH]