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To whomsoever it may concern,<BR> <BR>I am trying to create the tip6p itp file. In order to do that, since it is an overlap of the tip4p and tip5p model (visually)<BR>I am trying to understand the a, b, and c values for the position of the dummy charge in the tip5p models.<BR> <BR>Below is the part of the script that is of my concern.<BR>_________________________________________________________<BR><SPAN lang=EN-AU>[ dummies3 ]<BR>; The position of the dummy is computed as follows:<BR>;<BR>; The distance from OW to L is 0.07 nm, the geometry is tetrahedral<BR>; (109.47 deg)<BR>; Therefore, a = b = 0.07 * cos (109.47/2) / <STRONG>| xOH1 + xOH2 |</STRONG><BR>; c = 0.07 * sin (109.47/2) / <STRONG>| xOH1 X xOH2 |</STRONG><BR>; =20<BR>;<BR><STRONG>; Using | xOH1 X xOH2 | = | xOH1 | | xOH2 | sin (H1-O-H2)</STRONG><BR><STRONG>; | xOH1 + xOH2 | = 2 | xOH1 | cos (H1-O-H2)</STRONG><BR>; Dummy pos x4 = x1 + a*x21 + b*x31 + c*(x21 X x31)<BR>; Dummy from funct a b c<BR>4 1 2 3 4 -0.344908 -0.344908 -6.4437903493<BR>5 1 2 3 4 -0.344908 -0.344908 6.4437903493<BR>_______________________________________________________<BR> <BR>I do understand everything except the bolded bit.<BR> <BR>so far i have understood that |xOH1| is the magnitude of OH on the x-axis, but putting those values in i don't the the correct a, b, c.<BR>I'm not good in vectors and i have had a look at the gromacs manual (the 3out model ni figure 4.16).<BR> <BR>I don't know where i am going wrong. <BR> <BR>I would appreciate the help thanks.<BR> <BR> <BR>Thanks,<BR> <BR>Pratik Kaku<BR></SPAN><BR> </div></body>
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