[gmx-users] dummy constant calculations

[Arturas]

I am stucked on the calculations of a, c and c constants for dummies
in 'tip5p.itp' file. I could not get the same or very similar values
as the numbers in the file. However, theres is still unclear points.


a=b= 0.07 * cos(109.47/2) / | xOH1 + xOH2 |, where | xOH1 + xOH2 | =
= 2 | xOH1 | cos (H1-O-H2).

I assume that:
2 | xOH1 | cos (H1-O-H2) == 2 * xOH1 * cos(H1-O-H2)         ????
H1-O-H2 = 109.47, because there is a tetrahedral system.    ????
xOH1 & xOH2 = 0.1 nm , i.e. approximate O-H bond distance.  ????

Maybe I am interpret the math expression wrong ?


Arturas






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>> I checked 'tip5p.itp' file for how dummies were constructed.
>> Where I could find explanation how constants a, b , etc. are
>> calculated for topology ?
>> 
>> There are entries like  | xOH1 + xOH2 | and so on. xOH1 - does it
>> correspond to the O-H bond length ?
DvdS> Yes, but do check the manual as well...
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