Re: [ESPResSo-users] Verlet integrator motion equations

[Florian Weik]

Hello,

the integration function is in void src/core/integrate.cpp:214, integrate_vv(int n_steps, int reuse_forces),

the signle steps of the Velocity Verlet are actually in subroutines, which one does what can be seen from the comments.

The forces due to the Langevin thermostat can be found in src/core/thermostat.hpp:162 in inline void friction_thermo_langevin(Particle *p).

The relevant lines are starting at L292. By default we use flat noise and not Gaussian distributed.  We use the classical RAN1 PRNG,

cf. Press, W.H. and S.A. Teukolsky, 1992; Portable Random Number Generators, implemented in src/core/random.hpp:81 for long integers, which

is converted to a double in the same file in the function d_random.

Cheers,

Florian

On Mon, Mar 2, 2015 at 1:27 PM, Evyatar Arad <address@hidden> wrote:

Hello,

I am running NVT simulations with the Langevin thermostat. 

I would like to know where in the code are the Verlet-like equations of motion (namely, including friction and noise) for the new position and velocity of the particles. 

Lastly, I would also appreciate it if you tell me which Gaussian random number generator is used.

Once again, thanks in advance.

Evyatar.

--

Florian Weik, Dipl.-Phys.,
Institut für Computerphysik, Allmandring 3, D-70569 Stuttgart
Phone: +49-711-685-67703

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