Hi MagnusL, thank you for your suggetions. I added additional frames and histogram overlap much better and the the initial curve become much smoother.
But here is another problem that I could not solve. Between histogram 7 and 8 (red arrow), which correspond to frame186 and 187, respectively the distance between the two frame is only 0.015 nm.
Should I do longer pulling time to increase the frames that sampling more frequently around these two frames? Should it help?
Also can I use different k value for different frame, as I don’t want to rerun the whole simulation with higher k value.
Update: I just found a previous post discussing this.
I will update this post when I got this area sampled!
Thank you for your help!