[CP2K-user] [CP2K:18438] Re: SG-CPMD - Thermalisation problem

Simone Ritarossi sim.ritarossi at gmail.com
Sat Feb 11 00:33:42 UTC 2023

Dear Marcella, 
is the setting I proposed to "force" titanium atoms to thermalise at 600K 
(i.e. without giving a NOISY_GAMMA_REGION , keeping the LANGEVIN and 
without TEMP_TOL) equivalent to not defining a thermal region for titanium 
atoms? In other words: is making the temperature of 600K explicit for 
titanium atoms a non-trivial definition of a thermal region?

Many thanks in advance,

Il giorno venerdì 10 febbraio 2023 alle 16:54:11 UTC+1 Marcella Iannuzzi ha 

> Dear Simone 
> It is all correct. The keyword TEMPERATURE within the thermal region is 
> used for initialisation of the velocities
> Kind regards
> Marcella
> On Friday, February 10, 2023 at 2:48:21 AM UTC+1 Simone Ritarossi wrote:
>> Dear Marcella,
>> Thanks for your reply. I want to ask you for some clarification on the 
>> input part to be added:
>> 1) If I set DO_LANGEVIN_DEFAULT F and DO_LANGEVIN F I am associating my 
>> thermal region with an NVE molecular dynamics, right? I just want to 
>> "force" the titanium atoms to thermalise at 600 K, respecting a LANGEVIN. I 
>> must therefore choose .TRUE., right?
>> 2) If I exclude NOISY_GAMMA_REGION, I am associating the thermal region 
>> with the NOISY_GAMMA_REGION chosen on the total system, right?
>> 3) TEMP_TOL helps me with thermalisation, however doesn't this create 
>> 'non-physical' molecular dynamics, i.e. molecular dynamics from which I 
>> cannot extract dynamic properties such as the diffusion coefficient?  
>> 4) About LIST: I follow the implicit numbering of the atoms in the input 
>> file, right?
>> Many thanks in advance,
>> Simone
>>        &DEFINE_REGION
>>              DO_LANGEVIN T
>>              LIST  n1..n2
>>              TEMPERATURE     600
>>              #NOISY_GAMMA_REGION     2.1999999999999998E-04
>>              #TEMP_TOL 50
>> Il giorno mercoledì 8 febbraio 2023 alle 11:59:56 UTC+1 Marcella Iannuzzi 
>> ha scritto:
>>> Dear Simone, 
>>> You may define the thermal regions and set tuned  noisy gamma for each 
>>> region independently.
>>> CP2K_INPUT <https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT.html>
>>>  / MOTION 
>>> <https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT/MOTION.html> / MD 
>>> <https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT/MOTION/MD.html>
>>> <https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT/MOTION/MD/THERMAL_REGION.html>
>>> <https://manual.cp2k.org/cp2k-2022_1-branch/CP2K_INPUT/MOTION/MD/THERMAL_REGION/DEFINE_REGION.html>
>>> Regards
>>> marcella
>>> On Monday, February 6, 2023 at 5:25:48 PM UTC+1 sim.ri... at gmail.com 
>>> wrote:
>>>> Dear cp2k-users,
>>>> I have thermalisation problems with my heterostructure, consisting of a 
>>>> GST + TiTe2 (633 atoms), where I consider van der Waals interactions (with 
>>>> DFT-D3). Initially I have a relaxed structure (CELL_OPT), which I want to 
>>>> thermalise at 600K. I am using the SGCPMD (&LANGEVIN). The problem is that 
>>>> the titanium atoms do not thermalise at 600K, but at a lower temperature, 
>>>> whereas the other atoms do so acceptably. I have also tried thermalising 
>>>> initially with an NVT and then using SGCPMD, but the problem persists. 
>>>> I cannot use TEMP_TOL so as not to affect dynamic properties such as 
>>>> diffusion etc etc.
>>>> This also happens at 1300K (melting of GST). 
>>>> In general, I have tried different gamma values. 
>>>> I attached the input file.
>>>> Many thanks in advance,
>>>> Simone

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