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Re: [ESPResSo-devel] Particle Masses definition
From: |
Ulf Schiller |
Subject: |
Re: [ESPResSo-devel] Particle Masses definition |
Date: |
Mon, 22 Jun 2015 13:11:10 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 |
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