[gmx-users] High Pressure with Martini system

[Ricardo O. S. Soares]

Dear colleagues, 

I ran an NVT equilibration of a 24mi CG Martini atoms and detected the formation of vacuum spots on the solvent. 
However, the log file shows a very large negative pressure (about -4e+28) all the time, since the beginning. 
Despite the negative pressure, when I turn pressure coupling ON, the very first step causes the box to expand (!) too much and then the simulation crashes. 
Things I tried, and failed: changed the tau_p to several values (1 to 500); changed the compressibility; changed the ref_p from 1 to values closer to the starting pressure; changed time-step from 0.02 up to 0.0005. 
Additional info: used the insane.py script to solvate the box with polarizable water; there's a large (frozen) bilayer at the center of the box, It, however is smaller than the box sides, to it doesn't interact with itself via PBC. 
I'm sure I could provide more info, so please ask me for the specifics and I'll reply. 

Thanks, 

Ricardo. 

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Biological Chemistry and Physics 
Faculty of Pharmaceutical Sciences at Ribeirão Preto 
University of São Paulo - Brazil