[CP2K-user] [CP2K:17542] Temperature in NVT AIMD rised to extermely high

[Lucas Lodeiro]

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 (<wangchuyan123 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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