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

[Ben Hourahine]

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
> <mailto: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 <mailto:benjamin.hourahine at strath.ac.uk>
>
>     The  Department is  a partner  in SUPA,  the Scottish
>                 Universities Physics Alliance
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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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