Particle size and time scale

[Ahmad Reza Motezakker]

Dear EspressoMD users,

I have a polymer system coupled with LBM in espressomd. The problem is that particle dynamic is around 10^3 or 10^4 times faster than predicted results from predicted theory and previous resulted results. I have considered each sigma σ equal to 10 nm in reality or SI units. In other words, for a particle with length of 150 nm , I have considered 15 beads with σ =1 . 

Following that, the box lengh of 450 nm is set to 45 in espresso unit in the same way. All the rest of parameters have been calculated according to the mass of particle and the length unit of 10 nm.

Calculating time unit, I come up with time unit of [t]=9*10^-9 seconds. When it comes to running the simulation, I should set time step to maximum 0.001 (which will be equal to pico seconds in SI) to run, for bigger ones it crashes. And the result which I get from the simulation, it shows that the dynamic is so fast compare to theory. 

I will be really thankful if you share with me your thoughts and show me what I am doing wrong here. Thank you all in advance.

P.S. , I log the data each 1000 step which will be around nano seconds roughly.

Best regards,

Ahmad Reza