<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:'times new roman', 'new york', times, serif;font-size:12pt"><div>Hi,</div><div> I am planning to add an external harmonic potential along z direction of a system : i.e U(z)= 0.5*K*z(**2)</div><div>I was wondering if I can get an help on how to add an user-defined external potential like this in gromacs ? </div><div>Thanks</div><div>Sanku</div><div style="position:fixed"></div>
</div><br>
</body></html>