Sv: Re: [gmx-users] surface simulation

2008-11-03 Thread Peter Ahlström
If vapour pressure is not too high, I think it is physically more
relevant to simulate a CCl_4
slab with periodic boundary conditions suck that you get an infinite
2-slab repeated in the third 
dimension such that you get a vapour slab in between (surface tensions
etc are normally 
measured in equilibrium with the vapour). So, in my opinion, the easiest
thing to do is to simulate 
a slab of CCl_4 together with the vapour (at least you get less
artefacts from bad wall models
in that way). At least that is a somewhat physical system. Normally I do
not think that position
restraints are needed (but I have no experience with CCl_4)

Cheers,
Peter


Dr. Peter Ahlström
School of Engineering
University of Borås 
SE-501 90 Borås
Ph. +46-33-435 46 75 Fax +46-33-435 40 08
[EMAIL PROTECTED]
 Mark Abraham [EMAIL PROTECTED] 08-11-03 05:08 
Hongyan Xiao wrote:
 Hi, Mark Abraham,
  
 I accepted your suggestion on the language.
  
 I simulated the CCl_4 surface system. In order to simplify model,
using 
 the vacuum replaced the gas phase. Furthermore, I found some paper by 
 other people also deal with the gas/liquid using the vacuum. In 
 vacuum/CCl_4 , can I control the CCl_4 molecule not to run to the
vacuum 
 using the gromacs? For example, using the wall, but I do not set up
wall 
 parameters well. Please give me some suggestion. Thanks again!

Some position restraints will keep your surface intact. See the manual 
for details. GROMACS will report how much energy is going from the 
restraints and you should check your parameterization by seeing that 
this energy is pretty small.

Mark
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[gmx-users] surface simulation

2008-11-02 Thread Hongyan Xiao
Hi, all gmx-users,

 I was simulating a CCl4 surface system. I encounter some problems. I hope 
for your help.
 
First I built a 3x3x3 nm3 CCl4 box, then solved it into a  3x3x15 box in 
order to form gas/CCl4/gas surface system. After simulating in NVT, two CCl4 
molecules run away to the gas phase. I want to know how to control CCl4 not 
to run to gas phase. I used the gromos96 force field. Can you help me?
 
I expect your answer. Thanks a lot!

H. Y. Xiao 
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Re: [gmx-users] surface simulation

2008-11-02 Thread Mark Abraham

Hongyan Xiao wrote:

Hi, all gmx-users,
 
 I was simulating a CCl_4 surface system. I encounter some problems. I 
hope for your help.
 
First I built a 3x3x3 nm^3  CCl_4 box, then solved it into a  3x3x15 box 
in order to form gas/CCl4/gas surface system. After simulating in NVT, 
two CCl_4 molecules run away to the gas phase. I want to know how to 
control CCl_4  not to run to gas phase. I used the gromos96 force field. 
Can you help me?


I don't follow. What's the gas? Anyhow, it seems your CCl_4 surface is 
sublimating, which might not be surprising.



I expect your answer. Thanks a lot!


I suspect this is just a language issue, but expect in English carries 
the implication that someone is obliged to make an answer. All of us 
here who might answer your email are volunteers. A paragraph like I'll 
look forward to any answers. Thanks a lot! will avoid annoying people :-)


Mark
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[gmx-users] surface simulation

2008-11-02 Thread Hongyan Xiao
Hi, Mark Abraham,
 
I accepted your suggestion on the language. 
 
I simulated the CCl4 surface system. In order to simplify model, using the 
vacuum replaced the gas phase. Furthermore, I found some paper by other 
people also deal with the gas/liquid using the vacuum. In vacuum/CCl4, can I 
control the CCl4 molecule not to run to the vacuum using the gromacs? For 
example, using the wall, but I do not set up wall parameters well. Please 
give me some suggestion. Thanks again!
 
H. Y. Xiao

 
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Re: [gmx-users] surface simulation

2008-11-02 Thread Mark Abraham

Hongyan Xiao wrote:

Hi, Mark Abraham,
 
I accepted your suggestion on the language.
 
I simulated the CCl_4 surface system. In order to simplify model, using 
the vacuum replaced the gas phase. Furthermore, I found some paper by 
other people also deal with the gas/liquid using the vacuum. In 
vacuum/CCl_4 , can I control the CCl_4 molecule not to run to the vacuum 
using the gromacs? For example, using the wall, but I do not set up wall 
parameters well. Please give me some suggestion. Thanks again!


Some position restraints will keep your surface intact. See the manual 
for details. GROMACS will report how much energy is going from the 
restraints and you should check your parameterization by seeing that 
this energy is pretty small.


Mark
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