[CP2K-user] [CP2K:19382] Optimizing with TIP3P a water cluster model

['Vittorio Bariosco' via cp2k]

Dear Matthias,

Thank you very much for your answer. I will surely try it.

Best,

Vittorio

Il giorno mercoledì 18 ottobre 2023 alle 16:39:43 UTC+2 Krack Matthias ha 
scritto:

> Dear Vittorio
>
>  
>
> a CP2K input file for 32 TIP3P water molecules is attached.
>
> I plan to provide template CP2K inputs for the common 3- and 4-site rigid 
> and flexible water models in the CP2K data folder soon. I will announce 
> that here when done.
>
>  
>
> HTH
>
>  
>
> Matthias
>
>  
>
> *From: *'Vittorio Bariosco' via cp2k <cp... at googlegroups.com>
> *Date: *Tuesday, 17 October 2023 at 17:19
> *To: *cp2k <cp... at googlegroups.com>
> *Subject: *[CP2K:19377] Optimizing with TIP3P a water cluster model
>
> Dear CP2K users,
>
>  
>
> I have been through different threads on this forum to understand how to 
> optimize a cluster of 600 hundred atoms (see 0_tip3p_geom.xyz) with TIP3P 
> model.
>
>  
>
> 1)I firstly tried this input taken from the FIST repository on GitHub here 
> <https://github.com/cp2k/cp2k/blob/master/tests/Fist/regtest-4/H2O-1.inp>
>
> (see first_tip3p.inp) but I was always getting this error after the 
> Optimization starts:
>
> "WARNING| Particles:     600    598 at distance [au]:     1.82837959 less 
> than:      2.00430963; increase EMAX_SPLINE.
>
> GEOMETRY wrong or EMAX_SPLINE too small!"
>
>  
>
>  
>
>  
>
>  
>
> 2)The I moved to the other input reported in the same repository at this 
> link 
> <https://github.com/cp2k/cp2k/blob/master/tests/Fist/regtest-4/H2O-32_SPME_fp.inp.>
> , where more water molecules were included in the initial geometry. In 
> this case (see second_tip3p.inp),  the optimization starts but at a certain 
> point it crashes again with a similar error: 
>
>  
>
> "WARNING| Particles:     600    598 at distance [au]:     0.89796367 less 
> than:      0.95400000; increase EMAX_SPLINE."
>
> GEOMETRY wrong or EMAX_SPLINE too small! 
>
>
>
> At this point I am a little confused on how to proceed. I remembered that 
> tip3p is a rigid FF and I started to look for constraining options for 
> intramolecular distances and angles. I found in the same input of the above 
> the section &CONSTRAINT &G3X3.
>
>  
>
> 3) Thus, I defined the new input using this constrain that could probably 
> explains the reason why CP2K was crushing before in this way (see 
> third_tip3p.inp). However, also this test was unsuccessful with the 
> following error:
>
>  
>
> "    |  Error in constraints setup!
>
>     |  A constraint has been defined for a molecule type
>
>     |   but the atoms specified in the constraint and the atoms defined for
>
>     |   the molecule DO NOT match!
>
>     |  This could be very probable due to a wrong connectivity, or an error
>
>     |   in the constraint specification in the input file.
>
>     |   Please check it carefully!"
>
>  
>
> Moreover, I also found in another thread here 
> <https://groups.google.com/g/cp2k/c/ld5pmmYUnBk/m/iZte7XZGBwAJ>, that the 
> specified constrained keyword works only for MD runs and not for GEO_OPT or 
> CELL_OPT. 
>
>  
>
> At the moment I don't have any clue in how to proceed to obtain a 
> optimized geometry with tip3p model. For this reason I would like to ask if 
> anybody have ever optimized with tip3p model, or can help me for setting 
> the proper input.
>
>  
>
> Hope to hear from you.
>
>  
>
> Kindly,
>
>  
>
> Vittorio
>
>
>
>
>
>  
>
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