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Dear all,
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<div>I'm trying to define modified morse potential in Gromacs to be used as a forcefield using tabulated potentials.</div>
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<div>My potential's functional form is as: <span style="background-color: rgb(249, 249, 249); font-family: sans-serif; line-height: 19px; ">ε Exp[-2A(r-r*)] -2 </span><span style="background-color: rgb(249, 249, 249); font-family: sans-serif; line-height: 19px; ">ε
Exp[-A(r-r*)]</span></div>
<div><span style="background-color: rgb(249, 249, 249); font-family: sans-serif; line-height: 19px; "><br>
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<div><span style="background-color: rgb(249, 249, 249); "><font face="sans-serif"><span style="line-height: 19px; ">So I have to define g® = </span></font></span><span style="background-color: rgb(249, 249, 249); font-family: sans-serif; line-height: 19px; ">ε
Exp[</span><span style="background-color: rgb(249, 249, 249); "><font face="sans-serif"><span style="line-height: 19px; ">-2A(r-r*)] and h®=</span></font></span><span style="background-color: rgb(249, 249, 249); font-family: sans-serif; line-height: 19px; ">-2 </span><span style="background-color: rgb(249, 249, 249); "><font face="sans-serif"><span style="line-height: 19px; ">ε
Exp[-A(r-r*)]. They have to be defined as values in a xvg table where the table is filled with values of r, f®, f'®, g®,….</span></font></span></div>
<div><font face="sans-serif"><span style="line-height: 19px; ">My question is how can I make vales of these functions, while there's a variable in the exponential term. </span></font></div>
<div><font face="sans-serif"><span style="line-height: 19px; ">I saw in the manual on the </span></font><a href="http://www.gromacs.org/Documentation/How-tos/Tabulated_Potentials#Constructing_the_Table(s)">website</a><font face="sans-serif"><span style="line-height: 19px; "> noting
that h® for buckingham is expressed as h®=AExp[-Br] so I was wondering how they make the table of h® values while B is a variable.</span></font></div>
<div><font face="sans-serif"><span style="line-height: 19px; "><br>
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<div><font face="sans-serif"><span style="line-height: 19px; ">Solutions which cam ego my mind were:</span></font></div>
<div><font face="sans-serif"><span style="line-height: 19px; ">Should we use some </span></font><span style="font-family: sans-serif; line-height: 19px; ">mathematical approximations like Exp[-u]=1-u.</span></div>
<div><font face="sans-serif"><span style="line-height: 19px; ">or simply tabulated potentials does not support potentials more complex than lennard jones, and Buckingham is an integrated feature which doesn't need the xvv table.</span></font></div>
<div><font face="sans-serif"><span style="line-height: 19px; ">Any suggestions will be appreciated</span></font></div>
<div><font face="sans-serif"><span style="line-height: 19px; "><br>
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<div><font face="sans-serif"><span style="line-height: 19px; ">regards</span></font></div>
<div><font face="sans-serif"><span style="line-height: 19px; ">Reza </span></font></div>
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