[gmx-developers] wrong dhdl with lj-pme

[Igor Leontyev]

Sorry, the link https://gitlab.com/gromacs/gromacs/-/issues
Does not work for me. I have created an account at gitlab,
but it results in PAGE NOT FOUND


>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

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