high pressure

From: tillmann.utesch_at_mail.tu-berlin.de
Date: Thu Mar 11 2010 - 06:01:06 CST

Hi all,

I run a NPT simulation of an enzyme on a SAM coated gold surface.
During the simulation all gold atoms were fixed to their positions.
The total system is neutrally charged, but the head-groups of the
monolayers are positively and the gold atoms are negatively charged.
So the charges are not able (gold) or limited (SAM) in moving.
The simulations are very stable, but the the pressure is fluctuating
around a very high value. For the pressure control I used the Langevin
piston method. Forces between fixed atoms were ignored and for the
electrostatic interactions I used the PME summation.
Exclusion of gold and SAM atoms of the pressure calculations did not
change the very high pressure in the system.
What shall I do now? Is the high pressure a result of the high charge
density in the SAM and the gold? How can a modify my system to get
normal pressure values?


Tillmann Utesch
Institut für Chemie, Max-Volmer-Laboratorium
TU Berlin, PC 14
Straße des 17. Juni 135
D-10623 Berlin
Tel. +49-(0)30-314-26389

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