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Thank you for you quick answer because I've started to become crazy.
I'll see more carefully your preparation of the system( to be honest I
don't understand it) , but I can't see
why it shoud be faster to reach the equilibrium or even reach it and my
way or preparing the system isn't a properly way. There's any
explanation?<br>
Do you know where I can find a properly and well known arametrized
fatty acid for make some tests?<br>
<br>
Thanks again. Hector<br>
<blockquote cite="mid20050118145239.D49059-100000@qt.dq.ufscar.br"
type="cite">
<pre wrap="">On Tue, 18 Jan 2005, Hector Mtz-Seara wrote:
sorry Hector, my mistake: g_energy actually displays surface tension,
the equation I referred to is meant to convert surface tension into
surface pressure, which is the most common way to present an isotherm
(surface pressure against area per molecule). anyway, a surface tension
larger than that of water means that your system is not equilibrated
yet (it gives a negative surface pressure).
</pre>
<blockquote type="cite">
<pre wrap="">Sorry after reading again and again there is one question I'm not sure
about.
</pre>
<blockquote type="cite">
<pre wrap=""><>
g_energy output gives surface pressure, not surface tension.
</pre>
</blockquote>
<pre wrap="">I've been reading the gromac's manual an in 7th character , page 138 ,
first paragraph, it speaks about surface tension, not surface pressure.
In the option list of g_energy also speaks about #Surf*SurfTen. Then why
you say the output is the surface pressure?. If you are right then where
is the value of the surface tension of the water to make this output in
the gromacs program. By the way it then means that you can only
calculate "surface pressure" for monolayers in pure water systems?. Can
you explain me that a little more.
</pre>
</blockquote>
<pre wrap=""><!---->
no, it means that you need to know the surface tension of the subphase,
whether it is pure water or any other substance or even a solution.
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap=""><>to compute the <><>surface tension you have to use the standard
expression:
gama = gama_0 - pi
where:
gama = surface tension
gama_0 = pure water surface tension
pi = surface pressure
anyway, if you're getting surface pressures 3-fold larger than that
of pure water, then your surface tension is negative, isn't it? if
that happens to be the case, then your systems may be still away
from mechanical equilibrium.
maybe you could give some more details of your simulations: how did
you assembled each monolayer? how long was each simulation run? if
you plot surface area along the simulation time, is it stable?
</pre>
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<pre wrap=""><!---->
/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/
Dr. Andre' Farias de Moura
/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/
Laboratorio de Quimica Teorica
Universidade Federal de Sao Carlos
Sao Carlos - SP - Brasil
/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/-/
Endereco Atual
Grupo de Quimica Quantica
Instituto de Quimica de Sao Carlos
Universidade de Sao Paulo
Sao Carlos - SP - Brasil
Telefone: 55-16-3373-8055
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