Re: zeroMomentum for water droplet

From: Axel Kohlmeyer (akohlmey_at_gmail.com)
Date: Tue Dec 03 2013 - 22:38:16 CST

On Wed, Dec 4, 2013 at 12:38 AM, Mihaela Drenscko <quo.physics_at_gmail.com> wrote:
> Hi,
>
> I found that if I use zeroMomentum for water droplet on graphite, I can
> prevent drifting of water molecules towards adjacent cells. I keep the

this would be a *very* bad idea. zeroing the total momentum only
really is useful for a bulk liquid system to remove a drift which can
lead to the so-called "flying ice cube syndrome". if you would enable
this for a droplet you get very unphysical behavior. if a water
molecule will (partially) leave the droplet, it will be subject to
huge momentum fluctuation because of leverage imposed by this
algorithm.

if you want to confine water molecules you will be best of to define a
reflective boundary wall using tclBC.

axel.

> Carbon atoms fixed, that why when I run simulation with namd, I get the
> following message:
>
> ------------- Processor 0 Exiting: Called CmiAbort ------------
> Reason: FATAL ERROR: Cannot zero momentum when fixed atoms are present.
>
> Charm++ fatal error:
> FATAL ERROR: Cannot zero momentum when fixed atoms are present.
>
> Aborted (core dumped)
>
> How do I fix it?
>
> Thank you.
>
> Mihaela Drenscko

-- 
Dr. Axel Kohlmeyer  akohlmey_at_gmail.com  http://goo.gl/1wk0
International Centre for Theoretical Physics, Trieste. Italy.

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