Re: [ESPResSo-users] Correlation

[Wink, Markus]

Dear Roya,

 

concerning your questions:

1.  When you write time=[setmd time], what is the time that it gives you? What is its unit?

ESPResSo does not predefine any system of units. In a simulation you convert your parameters into MD units. This means that a timestep can correspond to any “physical-timestep”, depending on how you have chosen your setup. More information on “units in ESPResSo” can be found in the user’s manual.

 

3. I want to add Lattice Boltzman to my simulation and I need to see some sample codes about it or some projects on it. It really helps me since LB is complicated for me.

In the repository of Espresso, you will find an example of a lattice-boltzmann implementation (“object_in_fluid.tcl”). That, at least for me, is of great help to get an deeper understanding of the LB algorithm and implementation.

 

I hope that helps a bit (sorry, for the second question I don’t have an answer since I have never used it).

@ ESPResSo-experts: don’t hesitate to correct me, if anything is wrong in my answers!

 

Greetings

 

Markus

 

 

Von: espressomd-users-bounces+address@hidden [mailto:espressomd-users-bounces+address@hidden Im Auftrag von roya moghaddasi
Gesendet: Mittwoch, 23. April 2014 16:56
An: address@hidden
Betreff: [ESPResSo-users] Correlation

 

Hello everybody,

I have three questions:

1.  When you write time=[setmd time], what is the time that it gives you? What is its unit?

2. I have some polymers in my system and I want to calculate its velocity autocorreletion in order to find the  decay time or the time my system relaxes, so I write the following:

set vel [observable new particle_velocities type [list 0]]

set vacf1 [correlation new obs1 $vel corr_operation scalar_product tau_max 1 dt $time_step]

correlation $vacf1 write_to_file "vacf1.dat"

What it gives me in vasf1.dat is some lines like:

0 579900 11953.9
0.005 579899 11906.2
0.01 579898 11793.8
0.015 579897 11647.8

I don't know the meaning of each column. Of course I read the Espresso manual about it but I need more explanation, and I want to know how to find the decay time by these information.

3. I want to add Lattice Boltzman to my simulation and I need to see some sample codes about it or some projects on it. It really helps me since LB is complicated for me.

I would appreciate if someone can help me.

Thank you very much.

Roya