Re: net force applied on an object

[Jean-Noël Grad]

Dear Shammi,

To expand on Martin's excellent answer, you may also be interested in 
the Observables framework, which allows recording forces either manually 
in a python loop, or automatically as a function of time using the 
TimeSeries accumulator [1] with the ParticleForces observable [2]. If 
you need to write the force to a file automatically, there is also the 
H5md writer [3].

Best,
JN

[1] https://espressomd.github.io/doc4.1.4/analysis.html#time-series
[2] 
https://espressomd.github.io/doc4.1.4/espressomd.html#espressomd.observables.ParticleForces
[3] https://espressomd.github.io/doc4.1.4/io.html#writing-h5md-files

On 2021-12-18 11:15, Martin Kaiser wrote:
> Dear Shammi,
>
> in the documentation,
>
> https://espressomd.github.io/doc4.1.4/particles.html
>
> at point 4.3, you will find the command to access particle properties,
> which includes the force. In general the syntax is:
>
> system.part[<INDEX>].<PROPERTY>
>
> so for the force:
>
> system.part[<INDEX>].f
>
> This will give you an array of 3 values, which are the force in each
> spatial direction, x, y and z.
> You can simply use the numpy function:
>
> numpy.linalg.norm(force)
>
> ,where "force" is the array returned by espresso, to get the
> magnitude.
> Do this after each integration, or save the force values to a file, to
> do this analysis later for each time step.
>
> Best,
> Martin
> On Dec 18, 2021 09:07, Shammi Babar <babarshammi@gmail.com> wrote:
>
> > dear users,
> >
> > how to output net force applied on a particle at each step of
> > simulation?
> >
> > thanks