On 26/09/2011 6:25 PM, xiaojing gong wrote:
Hi, many thanks.
I am doing some simulation correlated with the growth, in experiments,
there are two kinds of growth, one is driven by kinetics and other is
by thermodynamics.
To address this question, I think you need to seek a better description
than "driven by thermodynamics". All processes are driven by thermodynamics.
So I just wonder to know by using MD simulations, the results I
obtained is driven by kinetics or thermodynamics.
The two growth modes must differ somehow in the conditions that trigger
them. For a valid model, which mode you might see will depend what
conditions you choose.
Mark
Silly question.
XJ
2011/9/26 Mark Abraham <mark.abra...@anu.edu.au
<mailto:mark.abra...@anu.edu.au>>
On 26/09/2011 5:31 PM, xiaojing gong wrote:
Hi, many thanks for your answer.
>> Any dynamical simulation has a lowest-energy structure...
whether this means anything is another question.
I am just wondering whether the structures you find with MD
determined mainly by thermodynamics (i.e. the lowest energy
structures) or by kinetics (i.e. the structures
with the lowest activation barriers)?
I wonder to know how can I set the parameters and in which
condition I obtain the structure by thermodynamics, and in which
condition (with which parameter setting) I can obtain the
structure by kinetics.
>> MD samples the free-energy surface. Its shape and the
temperature determine what structures might be found, and in what
proportions.
Do you mean that I can obtain the structure by thermodynamics in
longer and higher temperature ; obtain the structure by kinetics
in shorter and lower temperature?
You are drawing some artificial distinction whose purpose I do not
understand. A short simulation on a FES at a temperature low
enough that the barriers are larger than the readily available KE
will be kinetically trapped. I'd guess that most MD simulations
that have ever been run have suffered from this defect. The shape
of the FES will generally vary with temperature also.
Mark
2011/9/26 Mark Abraham <mark.abra...@anu.edu.au
<mailto:mark.abra...@anu.edu.au>>
On 26/09/2011 6:41 AM, xiaojing gong wrote:
Dear all,
A question about, in MD, in which situation you can
obtain a structure with lowest energy.
Any dynamical simulation has a lowest-energy structure...
whether this means anything is another question.
Can MD simulate the kinetics process, and obtain a
stuctrue with the lowest activation barriers?
Mapping free-energy surfaces where bonds are not made or
broken can be done with conventional MD.
Typically, are the structures we find with MD determined
mainly by thermodynamics or by kinetics ?
MD samples the free-energy surface. Its shape and the
temperature determine what structures might be found, and in
what proportions.
Mark
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