Hi Farideh

There no approach to find that, depends of your system. 30 Angstrom seems much for me! and take into account that you when your coordinate be out the electrostatic cutoff you set, the energy of the system will change. First, I recommend you to pull, we say, 5-6 A and see how the profile looks like. Best!

 You need "direction" geometry and a specified pull vector. The cylinder geometry may also be appropriate; the GROMACS manual has an example of exactly what you're doing, which you should use as a basis for your work. 

Dear Diego S. Vazquez,

Thanks for the clear answer.

Regards,

Farideh

Dear James “Wes” Barnett,

Hi,

Thanks for the time and answer.

Unfortunately, I cannot find your tutorial.

Regards,

Farideh

Dear Jamoliddin Razzokov,

Thanks for the answer. Actually, I used the direction_periodic instead of simple in pull_geometry and it worked but I am not sure if I should include any other changes or not.

Regards,

Farideh