[AMBER] calculating diffusion constants - multiplying factor (10/6)?

From: Vijay Manickam Achari <vjrajamany.yahoo.com>
Date: Mon, 1 Apr 2013 10:21:09 +0100 (BST)

Dear Sir/Madam,


Here I have a question on determining 'diffusion coefficient' from ptraj analysis for my bilayer system.

I used ptraj to calculate diffusion and I go four files such that fiilename_x.xmgr,  fiilename_y.xmgr, fiilename_z.xmgr, fiilename_r.xmgr,fiilename_a.xmgr.


ACTIONS

  1>  DIFFUSION
      Only the average results will be dumped to diff-malto-thermo.dat_?.xmgr
      The time between frames in psec is 5.000.
      To calculated diffusion constants, calculate the slope of the lines(s)
      and multiply by 10.0/6.0; this will give units of 1x10**-5 cm**2/s

During the run it is stated that, one must multiply with 10/6 to get the unit cm**2/s.

In literature it is stated that to calculate the diffusion coefficient, one must plot log vs log graph and find the slope (gradient) of the graph. And this slope represent diffusion coefficient.

I just want to get some clarification, do I need to times the factor (10/6) with the gradient value from log-log plot? Or I only need to multiply for the gradient calculated without log-log plot. 
Or is there any other way to to state?


Thanks in advance
Regards 

Vijay Manickam Achari
(Phd Student c/o Prof Rauzah Hashim)
Chemistry Department,
University of Malaya,
Malaysia
vjramana.gmail.com
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Received on Mon Apr 01 2013 - 02:30:03 PDT
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