|Subject:||[ESPResSo-users] is it possible to turn off inertia ?|
|Date:||Sun, 5 Feb 2017 16:01:18 -0500|
|User-agent:||Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0|
Dear all,Some of the projects I use Espresso for involve low Reynolds number/overdamped motion. In such cases, I have to make sure the system remains quasistatic, e.g. by allowing it to sufficient time to relax after applying a small perturbation. This can pose a problem when the relaxation times are long, sometimes resulting in unfeasibly long simulation times.
It seems to me that a lot of the computational effort is wasted when using the molecular dynamics framework in the case of overdamped motion. That is, if you could turn off inertia, you would just have to solve force = friction * v and not have to wait for the system to relax (?).
Making mass very small doesn't seem to help, since that introduces stability issues - you have to make the time step smaller, and you don't really gain anything. The solution (apart from writing your own code), as far as I can tell, is to change Espresso's code so it solves the force = friction * v equations of motions instead of doing Verlet integration (where inertia is implicit).
I'm wondering if people familiar with the code can assess whether this is feasible for me to do (does it just entail changing the code at one or a few places) or whether it's not worth trying because I would break and have to change too many things.
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