[DFTB-Plus-User] CouplingStrength in Nose Hoover thermostat

[simin pahlavi]

Dear Ben,
Thanks a lot for your helpful comments.
Best wishes
Simin

On Thu, Jun 4, 2020 at 8:05 PM Ben Hourahine <
benjamin.hourahine at strath.ac.uk> wrote:

> Hello Simin,
>
> if you are calculating vibration by autocorrelation or similar, its often
> a good idea to thermalize the simulation and then restart from final
> coordinates/velocities and then gather data in a constant energy simulation
> without a thermostat.
>
> I'd suggest 0.1 fs is probably safer for C-H stretch simulations (but
> perform a sensitivity test in a small system).
>
> Regards
>
> Ben
> On 04/06/2020 18:35, simin pahlavi wrote:
>
> Dear Ben,
> Thanks a lot for your prompt reply.
> I am working on vibration of carbon nanostructures saturated by hydrogens.
> I truly appreciate any comment regarding selecting the timestep. I thought
> 0.5 fs is a safe choice.
> Thanks in advance,
> Best regards,
> Simin
>
> On Thu, Jun 4, 2020 at 7:14 PM Ben Hourahine <
> benjamin.hourahine at strath.ac.uk> wrote:
>
>> Hello Simin,
>>
>> the coupling is relatively insensitive, so approximate the highest
>> vibrational frequency of the system will work OK.
>>
>> I would suggest testing the effect of the time step though, as  depending
>> on the properties you are interested in 0.5 fs seems a bit long for C-H
>> bonded systems (the thermostating will reduce sensitivity a bit though, as
>> accuracy in energy conservation is not required).
>>
>> Regards
>>
>> Ben
>> On 03/06/2020 15:32, simin pahlavi wrote:
>>
>> Dear DFTB users,
>> I have a question regarding Nose Hoover thermostat and I appreciate any
>> help.
>> I am performing Md using DFTB over a system of hydrocarbons ( C-H bonds)
>> and the time step is set to 0.5 fs.
>> I was wondering if the CouplingStrength [cm^-1] = 3000 in thermostat is a
>> good choice here.
>> Thanks in advance,
>> Simin
>>
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>> --
>>         Dr.  B.  Hourahine,  Senior  lecturer
>>             SUPA, Department  of  Physics,
>>              University  of  Strathclyde,
>>               John  Anderson  Building,
>>           107 Rottenrow, Glasgow G4 0NG, UK.
>>   +44 141 548 2325, benjamin.hourahine at strath.ac.uk
>>
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> --
>         Dr.  B.  Hourahine,  Senior  lecturer
>             SUPA, Department  of  Physics,
>              University  of  Strathclyde,
>               John  Anderson  Building,
>           107 Rottenrow, Glasgow G4 0NG, UK.
>   +44 141 548 2325, benjamin.hourahine at strath.ac.uk
>
> The  Department is  a partner  in SUPA,  the Scottish
>             Universities Physics Alliance
>
> The University  of Strathclyde  is a  charitable body,
>        registered in Scotland, number SC015263
>
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