[QE-users] how to generate metallic glasses through pw.x module md calculation

[Leonid Kahle]

Dear Song,


I'm not really an expert, but I hope this answer help you:

There is no such feature as an autopilot for PW to my knowledge.


I see three solutions:


A) You use the ion_temperature = 'reduce-T' (see 
https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm899). You can 
reduce the temperature every /nraise/ steps by /delta_t/. (which seems 
to do what you have in mind)
This will use the velocity rescaling thermostat.


B) If you want to use a different thermostat implemented, you can reset 
the temperature in an outer loop as in (bash):

for tempw in {1500..300..50}; do

     echo $tempw;

     sed -e "s/TEMPW/${tempw}" template.in > md_${tempw}.in

     mpirun -np X pw.x <md_${tempw}.in > md_${tempw}.out

done

Make sure each run restarts properly from the previous (including 
positions and velocities).
If you keep the same prefix and outfolder, than restart_mode='restart' 
will do what you want.


C) If, and only if, you are comfortable coding a bit in Fortan, and you 
have quite a complex temperature regime, you can go into 
PW/src/dynamics_module.f90

There, you will find a line:

IF ( control_temp ) CALL apply_thermostat()

For QE6.4.1 this is line 219, for example.

Before this line, you can reset the temperature as a function of the 
current MD-step.

temperature = complicated_function(istep)

I haven't tested this of course.


Best,


     Leonid Kahle


/Doctoral Assistant //EPFL STI IMX THEOS////CH-1015 Lausanne (Switzerland)/

On 6/17/19 4:55 AM, song Kingest wrote:
> Dear QE experts,
> I want to generate metallic glasses through qe. I am using the md 
> calculation in the pw.x module. It consists of three processes, 
> calculating 5000 steps in the case of 1500 K, reducing the system 
> temperature by 500 K every 20 steps, a total of 30,000 steps, and 
> finally calculating 5000 steps at 300 K.
> One question is how to link these three processes. I don't know how to 
> import the 1500 K calculation results into the cooling process for 
> calculation. Similarly, the second process to the third process has 
> similar problems.
> In the cp.x module, I found the AUTOPILOT function. This feature 
> allows for temperature changes during the simulation.
> AUTOPILOT
>      on_step =  31  : dt               = 5.0
>      on_step =  91  : iprint           = 100
>      on_step =  91  : isave            = 100
>      on_step = 191  : ion_dynamics     = 'damp'
>      on_step = 191  : electron_damping = 0.00
>      on_step = 691  : ion_temperature  = 'nose'
>      on_step = 691  : tempw            = 150.0
> ENDRULES
>
> However, the md calculation in the pw.x module does not have the 
> corresponding function. Therefore, I would like to ask if you have any 
> solutions?
> thank you all!😄
>
>
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