[lammps-users] addforce lammps

Dear all,
I want to apply fixed stress on one side of the nanotube keeping another side fixed For this I used, set force command to set force on the fixed side to zero while on the other side I am using and force of 16eV/A to impart forces on end atoms so that fixed stress will be applied. The main objective is to calculate elastic modulus with this. But something is going wrong in the script. If anyone please help me with this, it will be a great favor. I am attaching my script with this email.

1.in (1.75 KB)

5_5_50_SWBNNT.data (61.6 KB)

you have to be more specific than “something is going wrong”.
you are not only asking to have somebody else do your work for you, you also ask that person to first figure out what the problem is.

Sir,
I am sorry for not being specific. I am sorry if it really interprets that somebody else will do my work. The script is running without any error message. But, I am failing to apply force on another side of the nanotube. Because when I measure the change in length, I found there is no change as well as when I change the value of force then also the length is same.

upon taking a cursory look, there are several things in your input in your input that don’t make much sense or are not scientifically sound ( 1) first you heat up your system, then cool it down, 2) you use known to be bad thermostats for production use, 3) you apply fix temp/berendsen to all atoms, even though 3) in fact, why use a thermostat for this kind of study, there is nothing the object couples to? 4) ultra short simulation segments for equilbration and production).

but the issue of not seeing any effect of the added force is purely self inflicted. you have not time integration fix in the last part, so atoms cannot move. also you have:
fix 3 efgh addforce 0 0 16.0 every 1000

so the force is added only on every 1000th step, not on every step. but then you run only for 100 steps, so the force is added for at most 1 step, which cannot cause much change, even if you added a time integration fix. in general, this needs a lot of fixing and rethinking before you will get reliable and reasonable results.

clear cut case of GI-GO

axel.