[CP2K-user] [CP2K:11087] DFTB simulations of liquid water

hut... at chem.uzh.ch hut... at chem.uzh.ch
Thu Jan 3 14:47:21 UTC 2019


this phenomenon has been seen by us and others before. See
Choi et al., JPC B 117 5165 (2013). We have reparametrized
the gamma_H correction to get better results for pure water
(only published in the PhD of Yannick Misteli, chapter 3.7)

best 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: "cp2k" <cp... at googlegroups.com>
From: "Guillaume Stirnemann" 
Sent by: cp... at googlegroups.com
Date: 12/26/2018 04:33PM
Subject: [CP2K:11087] DFTB simulations of liquid water

Hi all, 

I am trying to simulate a box of liquid water using DFTB with periodic boundary conditions. My initial configuration is taken from a previous classical MD run performed in the NVT ensemble at the experimental density. 
I have tried different set-ups, including SCC-DFTB ("DFTB2") and DFTB3-diag, both with or without Grimme's D3 corrections, all ran in the NVT ensemble for 50 ps. 
In all cases, the simulations run well, but I end-up with a large hole in the simulation box. When comparing my radial distribution functions that of Cui who used DFBT+ (JPCB 115, 6790 (2011)), the first peak of the O-H rdf is usually a bit more pronounced but the contraction of the whole system is more visible on the second hydration shell. The differences are less visible for the O-O rdfs. The hole occupies about 1/2 of the simulation box, so the final density of my liquid phase is about 2! 

I attach the initial configuration, and the cp2k input file for DFTB2 with no D3. I tried on two different machines, one with 6.1 and the other one with 5.1. 

I am not an expert of CP2K so there might be some issues with my input, and your help would be very much appreciated. 

Best wishes

CNRS Institut de Biologie Physico-Chimique, Paris, France

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[attachment "input-DFTB2-gamma-noD.in" removed by Jürg Hutter/at/UZH]
[attachment "h2o.xyz" removed by Jürg Hutter/at/UZH]
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