[CP2K-user] [CP2K:17602] Temperature in NVT AIMD rised to extermely high

[Jessie wang]

Dear All,

I changed thermostat to CSVR/MASSIVE and timecon to 50, after 1 ps, the 
temperature goes down gradually. Then I changed the thermostat to NH/GLOBAL 
with timeco 1000, but for now the temperature is  too low for the system. I 
set the thermostat as 298.15K, and now it 250K. 
I wonder what's going on there, and what should I do to correct this.

I'd really appreaciate if anyone provide any comments.

Best,
Jessie


On Tuesday, August 30, 2022 at 10:32:02 AM UTC+8 nihar... at gmail.com wrote:

> Hi Jessie, 
> I think the best option is to run a short simulation using classical MD 
> and then start ab-initio simulation from the final configuration obtained 
> from the classical MD.
> Regards
> Niharendu
>
> On Thursday, August 25, 2022 at 3:42:41 AM UTC+5:30 Lucas Lodeiro wrote:
>
>> Hi Jessie,
>>
>> If your optimized geometry still get high temperature at the beginning of 
>> AIMD, maybe it reached a flat profile of the PES or a metastable structure 
>> with high energy. In this case I would run an AIMD with NH thermostat in 
>> the MASSIVE setting with a short timescale, to couple thightly each DoF 
>> with the thermostat, maybe this helps to thermalize the system, obviously 
>> after that you will need to equilibrate with a global thermostat and 
>> reasonable timescale.
>> It is reasonable that some solvent molecules fly out of the system when 
>> the temperature rises a lot.... With an equilibrated system this would not 
>> happen. By the way, there are restraints in CP2K to add confinement 
>> potentials.
>>
>> Regards - Lucas
>>
>> El mar, 23 ago 2022 a las 23:14, Jessie wang (<wangch... at gmail.com>) 
>> escribió:
>>
>>> Thank you Lucas. 
>>>
>>> I've applied  geo-opt before AIMD, temperature still rised a lot. But 
>>> now I know the temperature rising is because the initial geometry from your 
>>> advice. I'll try to improve initial geo. And it is also a good advice to 
>>> add D3 dispersion correction.
>>>
>>> I have another question, when we run AIMD, the outer sphere of water 
>>> molecules sometimes run too far away from our system, and actually, the box 
>>> is in a right size. What should I do to limit the motion of water to make 
>>> it not run too far.
>>>
>>>
>>> Best,
>>>
>>> Jessie
>>>
>>>
>>> On Wednesday, August 24, 2022 at 2:48:59 AM UTC+8 Lucas Lodeiro wrote:
>>>
>>>> As a first glance, the problem is probably located on your initial 
>>>> geometry... Packmol generates *good* solvation spheres, but they are far 
>>>> away from the minimal energy geometry, and probably the forces on atoms at 
>>>> the first step are very high. This explains why your kinetic energy rised a 
>>>> lot, a huge amount of potential energy is changing to kinetic energy. When 
>>>> I run this type of AIMD, usually relax the structure first with classic MD 
>>>> with OPLS-AA forcefield, to get a better geometrical guess to start the 
>>>> AIMD. Otherwise, you can do a geometrical relaxation (a non-tight 
>>>> relaxation) in ORCA at the same level to get a better geometrical guess. 
>>>> Also, I would add D3(BJ) dispersion correction to your calculation.
>>>>
>>>> Regards - Lucas
>>>>
>>>> El mar, 23 ago 2022 a las 13:57, Jessie wang (<wangch... at gmail.com>) 
>>>> escribió:
>>>>
>>>>> Dear all,
>>>>>
>>>>> I'm trying to do NVT AIMD for a system (a cluster surrounded by water 
>>>>> molecules). The water molecules was generated by packmol with tolerance 2.0.
>>>>> I was set temperature to 298.15K, but after several steps, it rised to 
>>>>> hundreds even thousands K.  I was used NOSE-HOOVER thermosat, and tried 
>>>>> CVSR also. it does not work.
>>>>>
>>>>>  Here I attached my input file, and any help would really appreciated. 
>>>>>
>>>>> Thanks
>>>>>
>>>>>
>>>>> Best,
>>>>> Jessie
>>>>>
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>>

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