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<div class="moz-cite-prefix">Hi,<br>
<br>
Acceleration groups will not work as those add an extra force to a
group and do not keep the total acceleration constant.<br>
<br>
I think that using a pull coordinate with absolute reference and
of constraint type should work, then you need to set a velocity
using the free-energy coupling with lambda and setting a pull
rate.<br>
<br>
Otherwise you can indeed use one of the two user groups.<br>
<br>
Cheers,<br>
<br>
Berk<br>
<br>
On 2020-04-10 13:01, Erik Lindahl wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAEJJM8EXeQTJELGePk_2S+08M-swfenJbq1ik5e-k1c17c+s-A@mail.gmail.com">
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<div dir="ltr">Hi Rebecca,
<div><br>
</div>
<div>I have to confess it was a _long_ time since I looked into
these parts of the code, but you might be able to achieve this
simply by defining a group, giving it the initial velocity you
want, and then using the constant-acceleration functionality
with the value 0.0 (since zero constant acceleration means
constant speed).</div>
<div><br>
</div>
<div>And if that fails, it should be possible to fix it without
too much effort :-)</div>
<div><br>
</div>
<div>Otherwise, the idea of the user groups is exactly that you
should be able to quickly implement a small routine where you
do something to an arbitrary group without having to redefine
the input mdp options, create a new (incompatible) TPR
version, and also having to modify the enum lists.</div>
<div><br>
</div>
<div>Cheers,</div>
<div><br>
</div>
<div>Erik</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Fri, Apr 10, 2020 at 12:55
PM Rebecca Kleemann <<a
href="mailto:rkleeman@students.uni-mainz.de"
moz-do-not-send="true">rkleeman@students.uni-mainz.de</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left-width:1px;border-left-style:solid;border-left-color:rgb(204,204,204);padding-left:1ex">
<div>
<p>Hi, <br>
</p>
<p>I want to add a group to set atoms to a constant
velocity.</p>
<blockquote>
<p><font size="-1" face="Courier New, Courier, monospace">enum<br>
{<br>
egcTC, egcENER, egcACC, egcFREEZE,<br>
egcUser1, egcUser2, egcVCM, egcCompressedX,<br>
egcORFIT, egcQMMM,<br>
egcNR<br>
};</font></p>
<p><font size="-1" face="Courier New, Courier, monospace">const
char *gtypes[egcNR+1] = {<br>
"T-Coupling", "Energy Mon.", "Acceleration",
"Freeze",<br>
"User1", "User2", "VCM", "Compressed X", "Or. Res.
Fit", "QMMM", nullptr<br>
};</font><br>
</p>
</blockquote>
<p>Are "User1" and "User2" meant to be used like that and
can they be renamed or should I add a new group and
increase the number of groups?</p>
<p>Greetings,</p>
<p>Rebecca<br>
</p>
</div>
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<div><br>
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-- <br>
<div dir="ltr" class="gmail_signature">
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div>
<div dir="ltr">
<div>Erik Lindahl <<a
href="mailto:erik.lindahl@dbb.su.se"
target="_blank" moz-do-not-send="true">erik.lindahl@dbb.su.se</a>></div>
<div>Professor of Biophysics, Dept. Biochemistry
& Biophysics, Stockholm University</div>
<div>Science for Life Laboratory, Box 1031, 17121
Solna, Sweden</div>
</div>
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