# [CP2K-user] [CP2K:18351] How to find the global minimum...?

'rabdel' via cp2k cp2k at googlegroups.com
Wed Jan 18 17:10:07 UTC 2023

```Hi,
You can try with this
approach: https://doi.org/10.1016/j.micromeso.2019.109885
Best regards,
Rabdel

El viernes, 29 de abril de 2022 a las 15:02:58 UTC+2, wave... at gmail.com
escribió:

> Hi
>
> In researching global optimization, I stumbled on a reply be Ole Schütt,
> who is the author of the SWARM part of CP2K. He suggested that the methods
> are somewhat older and to look at ASE <https://wiki.fysik.dtu.dk/ase/>. I
> think this is what I will look into.
>
> Cheers
> Sam
>
> On Friday, January 22, 2021 at 4:59:34 PM UTC+1 Monu Joy wrote:
>
>> Thanks, Fangyong for the suggestion.
>>
>> On Fri, Jan 15, 2021 at 10:01 PM Fangyong Yan <fyya... at gmail.com> wrote:
>>
>>> Hi, Monu,
>>>
>>> The difference energy is -6235.818 - (-6235.824) = 0.006 Hartree =
>>> 15.753 kj/mol.
>>>
>>> So if you use 800 K, the Boltzmann factor is: exp(-dE/R/T) =
>>> exp(-15.753*1000/8.314/800) = 0.09, which means you would have a
>>> probability of 0.09 to "jump" from the lower energy to higher energy, by
>>> the help of heat.
>>>
>>> So I think NVT at 800K, may be helpful for exploring the potential
>>> energy surface, even within 10ps.
>>>
>>> Regards,
>>>
>>> Fangyong
>>>
>>>
>>> On Fri, Jan 15, 2021 at 8:08 PM Monu Joy <monuj... at gmail.com> wrote:
>>>
>>>> Hi Lucas & Fangyong
>>>>
>>>> Thanks for the help. I have performed two cell-opt calculations of
>>>> guest at host where the following total energies respectively represent the
>>>> guest at the center of the MOF pore and near to the pore surface -6235.818
>>>> and -6235.824. Do you guys think that this energy difference is
>>>> reasonable...?
>>>>
>>>> Also, do you by chance have any reference that shows local minimum
>>>> geometry modulate the property of a system more effectively...?
>>>>
>>>> Thank you so much for your help!
>>>>
>>>> -Monu
>>>>
>>>>
>>>> On Wednesday, 13 January, 2021, 10:01:30 am GMT-5, Lucas Lodeiro <
>>>> eluni... at gmail.com> wrote:
>>>>
>>>>
>>>> Hi Monu and Fangyong,
>>>>
>>>> I disagree a little bit with Fangyong because an AIMD calculation is
>>>> not cheaper, and if the barriers between local minimas are high, you cannot
>>>> see a structural change with the MD, at least in the scale time of ps.
>>>> Firstly, I would try to optimize a couple of structures and measure the
>>>> energy differences, this will give you a little insight about the barriers
>>>> (the minimum energy for the barriers), If they are high, the AIMD probably
>>>> cannot move from one local minima to another. If they are little, you can
>>>> see the structural changes, but in this case, probably the global minima is
>>>> not sufficient to modulate the properties of the system, and some other
>>>> local minima have to be taken into account.
>>>> Other way is to generate with a script random positions of the molecule
>>>> into the MOF and minimize them with a semiempirical formulation, as XTB (
>>>> https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/QS.html#METHOD),
>>>> and rerun with the level of theory that you want just the low energy ones.
>>>>
>>>> Regards - Lucas Lodeiro
>>>>
>>>>
>>>> El mié, 13 ene 2021 a las 0:07, Fangyong Yan (<fyya... at gmail.com>)
>>>> escribió:
>>>>
>>>> Hi, Monu,
>>>>
>>>> To explore the free energy surface better, you may need to start at a
>>>> high temperature, and then annealing down to the room temperature. And for
>>>> each temperature, you can plot the radial distribution function, for your
>>>> guest molecule and your MOF atoms, for example, at 800 K, 700 K, ....,
>>>> 300K. The reason starting at high temperature is that you can use heat to
>>>> get your guest molecule out of the potentially trapped free energy minima,
>>>> so you can explore the free energy minima more completely.
>>>>
>>>> Regards,
>>>>
>>>> Fangyong
>>>>
>>>> On Tue, Jan 12, 2021 at 10:01 PM Fangyong Yan <fyya... at gmail.com>
>>>> wrote:
>>>>
>>>> Hi, Monu,
>>>>
>>>> You can run a molecular dynamics simulation at room temperature, for
>>>> several picosecond, and then you can plot the radial distribution function,
>>>> between your guest molecule and the MOF, by doing this you would have a
>>>> general picture of the free energy surface of your guest molecule in the
>>>> MOF. Then based on the free energy minima structures, you can start to
>>>> optimize your guest-MOF complex structure. (the free energy surface may be
>>>> different from the potential energy surface, but at least by doing MD
>>>> simulation and calculating the free energy surface based on radial
>>>> distribution function, you can have a basic idea about the free energy
>>>> surface, which should not be quite different from potential energy surface).
>>>>
>>>> Regards,
>>>>
>>>> Fangyong
>>>>
>>>> On Tue, Jan 12, 2021 at 7:20 PM Monu Joy <monuj... at gmail.com> wrote:
>>>>
>>>> Hi there
>>>>
>>>> I have a general question: I would like to find out the global minimum
>>>> of a guest molecule within the pore of a MOF. I know I can place the guest
>>>> molecule in the pore and get the host-guest structure optimized, but if I
>>>> would place the guest molecule in another position of the same pore, there
>>>> also I can get the structure optimized. In this scenario how could I find
>>>> the exact most probable location of the guest molecule within the MOF pore
>>>> or its global minimum...?
>>>>
>>>> Any help would be highly appreciated...
>>>>
>>>> -Monu
>>>>
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>> *Thanks with Regards*
>>
>

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