[gmx-users] how to build up fixed connections? how to simulate no electrostatics?

[Nicolas Schmidt]

(a) Nope, my .mdp-file don't reads that. So I think I don't use one.
(b) I use some different software, that does exactly what I want. It's 
very reliable and it's telling me that the pressure of a 2CLJ-fluid with 
all the set parameters should be different. Since I wanna do the exact 
same thing, the higher pressure kind of points out that in fact I'm not 
doing the same.
(c) Exactly! Bondtype 5 doesen't imply a length parameter. So therefor 
I'm using a constraint. David told me to do so. I'm really unsure at 
this point, this is why I posted my issue.

Still: Though I thought I don't have to specify the 
electrostatics-section since my molecule doesn't have any charges (or 
does it???), what to do to totally switch the electrostatics off?

Thanks to everyone.

David Mobley wrote:
> Maybe this is naive, but:
> (a) Are you using pressure regulation? (If so, with which barostat?)
> (b) How do you know what you expect the pressure to be?
> (c) By "fixed connections", do you mean fixed bond lengths? Are you
> doing this using constraints?
>
> David
>
> On 8/13/07, Nicolas Schmidt <nicolas-schmidt at gmx.de> wrote:
>   
>> Hey everybody.
>>
>> I'm still trying to biuld up a bulk of 2CLJ-molecules (ethane). I just wanna use fixed connections in-between the CH3-"atoms" and no eletrostatics during the simulation. I posted my .itp-file several times along my .top-file and my used .mdp-file. Though the simulation runs fine I'm unhappy with the results, cause pressure is higher than I expect it to be.
>>
>> Since Mark told me, I'm not simulating fixed connections I'd like to ask if ANYBODY could help me with that.
>>
>> Thanks in advance
>>
>> Nicolas
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