Re: [ESPResSo] mbtools-fluctuations-bending modulus

[Tristan Bereau]

Dear Martina,

I'm not sure about this, but it could be that the <|h(q)|^2> already contains 
the L^2 term. That way, you wouldn't have to multiply by it. What value of 
kappa do you get if you don't multiply by L^2? Just plot the power spectrum as 
you're doing now and calculate 1/a, where a is the value of the straight line. 
As far as I remember, you should get a value of kappa between 25 and 35 kT for 
a flat bilayer.

Best,
Tristan

On Jan 12, 2010, at 1:55 , martina pannuzzo wrote:

> Dear all,
> i need a clarification about the example fitting gnuplot script in the
> file fluctuation.tcl in the mbtools package.
> The k that you are calculating is the bending modulus ( express in
> units epslon)?  When i try to calculate the bending modulus plotting
> 1/q^-4 vs <|h(q)|^2> (of the power-dat file)  i obtain a constant that
> i moltiplicate for L^2, but i obtain a k value  different and
> completly wrong. Please, can anyone help me?
> thanks in advance.
> Martina
> 
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