Dear Chris,
I put one tip5p molecule in a center of dodecahedral box - 2nm from that molecule to walls, filled it with tip5p, ran 6000 steps of steep minimization. After another 2704 steps of cg it converged to emtol 1.0. I run 100k steps of nvt on this box afterwards (http://shroom.ibb.waw.pl/tip5p/pure1). But the water is very capricious. If I ran only 2000 steps of steep, the following cg crashed after less than 1000 steps because a water molecule could not be settled. I could not minimize another box, filled only by genbox from an empty gro file (http://shroom.ibb.waw.pl/tip5p/pure2). I understand that you have to have some luck if you run a simulation in pbc with rigid water, which interacts through walls of the box with the other side and was not well placed. Also, I had several segfaults during minimization that I was able to avoid only by limiting the number of cores. I checked distances between OW and LPx on a crashing minimization with a peptide - 2812 water molecules. Maximum force reached 8.8e+24 in 225 steep steps, but all the 5624 distances were rock solid 0.7A, as expected. I still did not post the redmine issue, I want to be sure that I am doing everything correctly.

On 2013-09-29 18:47, Christopher Neale wrote:
Dear Grzegorz:

Under no conditions should any of the tip5p geometry change (for the
standard tip5p model).
If you find that this is happening, then that is certainly an error.
You can check if you like by analyzing
your trajectory. However, flexible bonds will allow the distance from
the arginine N to the arginine
H to vary, which my allow a closer approach of the arginine H to the
tip5p dummy site.

Did you verify that a water box (no protein) simulates without error?

Did you post a redmine issue with .mdp , .gro , and .top files?

Chris.

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