[gmx-users] Energetics in collision

Erik Marklund erikm at xray.bmc.uu.se
Thu Apr 19 13:21:05 CEST 2007

19 apr 2007 kl. 12.50 skrev Janne Hirvi:

> Hello gmx-users!
> I am studying the effect of impact velocity of a water droplet in  
> collision with
> a frozen surface in NVE ensemble. A droplet has extra translational  
> energy,
> which corresponds to a specific velocity, in addition to thermal  
> energy at
> 300K.
> I supposed that at the collision extra translational energy of the  
> droplet will
> change to potential and kinetic energy of the droplet so that total  
> energy of
> the system is conserved. However, even I observe increase in  
> potential and
> kinetic energy, total energy of the system (~300 000kJ/mol) first  
> decreases
> slightly (<100kJ - exact value depends on the velocity) and just  
> after that
> reverts partly, but stabilizes value lower than at the beginning.

Don't know for sure, but incorrect comm removal springs to mind.

> The total energy should be conserved but on the other hand it  
> sounds logical
> that there will be stabilizing energy from the droplet-surface  
> interactions
> which prevents the droplet to bounce away and makes it to  
> equilibrate on the
> surface. I am wondering if this is the case or have I done some  
> mistake which
> disturbs the energy conservation?

Wouldn't that stabilizing energy be part of the total energy?

> The other question concerns about the intrusion of the droplet into  
> the pores of
> the structured surface. The situation is otherwise the same but now  
> the total
> energy continues to decrease after first touch and wont stabilize  
> until the
> bottom of the pore is reached. It again sounds like a consequence  
> of the
> stabilizing energy from the droplet-surface interactions, but now  
> when these
> interactions are larger than without the intrusion also slight  
> increase (2-3K)
> in the droplet temperature is observed. It sounds little bit  
> strange that water
> molecules in the pores would have higher temperature. So again is  
> it really the
> truth or have I done something what I shouldnt have?
> Thanks for your time and assistance,
> Janne
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Erik Marklund, PhD student
Laboratory of Molecular Biophysics,
Dept. of Cell and Molecular Biology, Uppsala University.
Husargatan 3, Box 596,	75124 Uppsala, Sweden
phone:	+46 18 471 4537		fax: +46 18 511 755
erikm at xray.bmc.uu.se	http://xray.bmc.uu.se/molbiophys

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