Re: [ESPResSo-devel] Particle Masses definition

[Evyatar Arad]

Thank you Ulf, Joost. That explains it.

Another thing i’ve been wondering about.
I’ve added two new particle properties to the code (in particle_data.pp), both 
are constant throughout the simulation.
Under void init_particle(Particle *part), i’ve tried assigning values to the 
two (both are dependant on langevin_gamma, PMASS and time_step) but it seems 
the real langevin_gamma are still at 0.0 rather then the 1.0 they later posses 
(while in the integration loop, for example).
In short, my question is where do you think is the right place to assign real 
values to the two, given their other variable dependencies?

Good day to you all,
Evyatar.

> On Jun 22, 2015, at 3:11 PM, Ulf Schiller <address@hidden> wrote:
> 
> On 22/06/15 12:34, Evyatar Arad wrote:
>> Good week all,
>> 
>> I’ve noticed that in friction_thermo_langevin there are two different masses 
>> used in the langevin equation while calculating force:
>>      p->f.f[j] = langevin_pref1*p->m.v[j]*PMASS(*p) + 
>> langevin_pref2*gaussian_random()*massf;
>> 
>> What is the difference between PMASS(*p) and massf?
>> both are available even though MASS (mass per particle) is off.
> 
> The variable `massf` is defined a few lines up in the code
> 
>  double massf = sqrt(PMASS(*p));
> 
> Note that the mass only enters this equation when the parameter gamma is
> not a proper friction coefficient but a relaxation time. See also
> https://savannah.nongnu.org/bugs/index.php?45349
> 
> Cheers,
> Ulf
> 
> -- 
> Dr Ulf D Schiller
> Centre for Computational Science
> University College London
> 20 Gordon Street
> London WC1H 0AJ
> United Kingdom
> 
>