[CP2K-user] [CP2K:15092] Re: Equation used for annealing

[Lenard Carroll]

I might be wrong, but for the NVE ensemble, T(n)=s^n * T(n=0) can be
derived directly from |v|(n)=q^n * |v|(n=0) if we write:
T(n) = (Σ[k=0→K] |v_k(n)|^2)/(3k(K-m)) = (Σ[k=0→K] |q^n
v_k(0)|^2)/(3k(K-m)) = q^n T(0)

So I should then be able to use T(n)=s^n * T(n=0) to find the value of s.
But when I tried this earlier, I got much different results. That's why I
just wanted to make sure my understanding of n in T(n) is correct.

In another case I am using a 20 fs time step and 1000 steps, equating to 20
ps. Is n still an element of [0,1000]?

On Thu, Apr 8, 2021 at 2:37 PM Lenard Carroll <lenardc... at gmail.com>
wrote:

> And this n, is this per MD step? For example, if I run the simulation for
> 20 ps with a time step of 2 fs [10000 steps], is n then an element of
> [0,10000]?
>
> On Thu, Apr 8, 2021 at 1:09 PM Julian Heske <jjh... at gmail.com> wrote:
>
>> Dear Lenard,
>>
>> your equation is true for the keyword TEMPERATURE_ANNEALING, which
>> modifies the target temperature of the thermostat each step and I would
>> suggest you to use this. The more general form is than
>>
>> T(n)=s^n * T(n=0).
>>
>> However, the ANNEALING parameter is for the velocities, so my guess is (I
>> never used it, please s.o. correct me if I'm wrong):
>>
>> |v|(n)= q * |v|(n-1)
>>
>> and
>>
>> |v|(n)=q^n * |v|(n=0).
>>
>> Using the relation T(n) ~ |v|(n)^2 (
>> https://en.wikipedia.org/wiki/Thermal_velocity ), you can also calculate
>> the impact of the scaling parameter q on the temperature if you want to use
>> this one.
>>
>>
>>
>> Best,
>> Julian
>> ASSIDUO Network schrieb am Dienstag, 6. April 2021 um 08:43:25 UTC+2:
>>
>>> Hi there everyone. Does anyone perhaps know the equation that is used
>>> for annealing (https://manual.cp2k.org/trunk/CP2K_INPUT/MOTION/MD.html).
>>> Here I know a scaling factor is multiplied to the initial temperature, but
>>> I don't know if it takes on the form of:
>>> T(n) = sT(n-1) or some other complicated equation.
>>>
>>> Could anyone let me know as I want to do the annealing properly.
>>>
>>> Much appreciated,
>>> Lenard
>>
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