Hi all,
I am a new ESPResSo user and I am trying to simulate a bilayer at different low tension values (say from 0 mN/m to 1 mN/m) using the Andersen barostat (turning npt "on"). It's not clear to me:
1) how membrane tension should be calculated (is it the average of the Pxx and Pyy components of the stress tensor? Does the calculation depend on whether I allow the box size to change in only x,y directions or x,y,z directions?)
2) is p_external the value in the attached simplebilayer.tcl file that I have to increase in order to increase the tension
3) what kind of fluctuation to expect in the tension since the tension is calculated from the virial pressure which has a lot of inherent fluctuations?
4) what range of parameters to use for the piston (mass, and friction coefficient)
5) are there any known convergence issues with using the barostat and does that mean I have to run the simulation for long simulation times?
Also, a more general question is whether the warmup is absolutely necessary or can I skip it?
Any help will be greatly appreciated.
main.tcl