[gmx-developers] wrong dhdl with lj-pme

[Paul bauer]

Hello,

can you please open an issue for this on 
https://gitlab.com/gromacs/gromacs/-/issues.

This looks like something that needs immediate attention for the 2020.2 
patch release.

Thanks!

Paul

On 06/04/2020 08:59, Igor Leontyev wrote:
>
> Dear gmx developers,
>
> 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."
>
>
> 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.
>
>
> Here are the numbers:
>
>               gmx-ver/vdw-type       <dVcoul/dl> <dVvdw/dl>
>
>               2020/PME                    -6.39450e-01 9.72647e+01
>
>               2020/CutOff                 -3.99985e-01 4.39876e+01
>
>                5.1/PME                    -3.08675e-01  4.36738e+01
>
>
> 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.
>
>
>

-- 
Paul Bauer, PhD
GROMACS Development Manager
KTH Stockholm, SciLifeLab
0046737308594

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