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<div class="moz-cite-prefix">Hello,<br>
<br>
can you please open an issue for this on
<a class="moz-txt-link-freetext" href="https://gitlab.com/gromacs/gromacs/-/issues">https://gitlab.com/gromacs/gromacs/-/issues</a>.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">This looks like something that needs
immediate attention for the 2020.2 patch release.<br>
<br>
Thanks!<br>
<br>
Paul<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 06/04/2020 08:59, Igor Leontyev
wrote:<br>
</div>
<blockquote type="cite"
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<p>Dear gmx developers,</p>
<p>In solvation free energy simulations with gmx 2020.1 I came
across the following issue. vdW component of dG and DHDL
values are ~2X overestimated at the lambda region in which
vdw-lambdas are changing. Additional testing has shown that
this issue is related to "vdw-type = PME."</p>
<p><br>
</p>
<p>I have compared (for lambda-state=4) <dVvdw/dl> results
of gmx2020 with vdw-type: PME and CutOff, with the result of
old gmx5.1 with vdw-type = PME. All was run on CPU for 5
nanosecs with PME electrostatics. It turned out that gmx2020
with vdw-type=CutOff reproduces (within the accuracy) the
<dVvdw/dl> result of gmx5.1 with vdw-type = PME, which
is expected. In the uniform environment both vdw-types should
give accurate solvation FE. The result of gmx2020 with
vdw-type=PME, however, is around 2X exaggerated, which seems
to be a bug.</p>
<p><br>
</p>
<p>Here are the numbers:<br>
</p>
<p> gmx-ver/vdw-type <dVcoul/dl>
<dVvdw/dl></p>
<p> 2020/PME -6.39450e-01
9.72647e+01</p>
<p> 2020/CutOff -3.99985e-01
4.39876e+01</p>
<p> 5.1/PME -3.08675e-01
4.36738e+01</p>
<p><br>
</p>
<p>Note, the problem is related to DHDL only, all potential
energy components (including vdW) in all runs are consistent.
Let me know if you need input files to reproduce the issue.
Though I believe, it can be observed for any simple solute in
water solution.</p>
<br>
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<br>
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<p><br>
</p>
<pre class="moz-signature" cols="72">--
Paul Bauer, PhD
GROMACS Development Manager
KTH Stockholm, SciLifeLab
0046737308594</pre>
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