CCL:G: MD with DREIDING FF: system becomes unstable on inclusion of charges

From: "Emmeline Yeo" <emma.yeo2704(-)gmail.com>
Subject: CCL:G: MD with DREIDING FF: system becomes unstable on inclusion of charges
Date: Tue, 16 Aug 2011 04:20:40 -0400

 Sent to CCL by: "Emmeline  Yeo" [emma.yeo2704|-|gmail.com]
 Hi everyone,
 I'm new to force field molecular dynamics and will appreciate any advice that
 you can give on problem that I have.
 I was trying to simulate an amorphous polyacetylene polymer cell using the
 DREIDING force field with the program dl_poly. The system is stable and runs
 well if I set the atomic charges for all my atoms to zero. However, once I
 include the atomic charges (calculated using Gaussian program - and I
 checked, the values are reasonable and similar to another published paper),
 the system just becomes out of control: the total energy and the temperature
 of the system becomes very high.
 I don't think the problem lies with a bad initial configuration for the
 polymer as the same thing happens even if I just have 2 polymer chains in my
 periodic cell.
 An advice that I've been given is to ignore atomic charges except in the
 cases of simulating polyelectrolytes...
 Any other suggestions given is deeply appreciated!