Equilibrating with Morse Bonds

I have a system in which some of the bonds are Morse bonds. I am having difficulty trying to equilibrate from the initial configuration.

I suspect the following problem may be common: Once an atom connected by a morse bond is far away from its equilibrium bond length, it almost has no tendency to go back because of the flat tail of the Morse bond potential. This makes equilibration more difficult because the forces can sometimes get so big in equilibration that the atoms move far away from their equilibrium positions and will never move back.

In addition to using nve/limit and/or a small timestep, do you have any tips to share?

Thanks.

I have a system in which some of the bonds are Morse bonds. I am having
difficulty trying to equilibrate from the initial configuration.

I suspect the following problem may be common: Once an atom connected by a
morse bond is far away from its equilibrium bond length, it almost has no
tendency to go back because of the flat tail of the Morse bond potential.
This makes equilibration more difficult because the forces can sometimes get
so big in equilibration that the atoms move far away from their equilibrium
positions and will never move back.

In addition to using nve/limit and/or a small timestep, do you have any tips
to share?

why don't you start with a harmonic bond and then
switch to morse, once the system is well enough
equilibrated. you can easily derive the suitable
harmonic parameters from the morse parameters
with an analytic procedure.

axel.