[gmx-developers] Conserved energy drifts more with shorter time steps

[David van der Spoel]

On 02/06/15 12:47, Berk Hess wrote:
> Hi,
>
> So this is not using SETTLE or LINCS?
> With SETTLE this is a known issue.
No this is flexible organic molecules at contant volume.

>
> Did you try running NVE?
How do we run more NVE than with the settings below?

>
> Cheers,
>
> Berk
>
> On 2015-06-02 12:43, David van der Spoel wrote:
>> Hi,
>>
>> this is in between a user and a developer query. We find that for
>> flexible liquid simulations using gromacs 5.0.4/single precision the
>> energy conservation gets WORSE with decreasing time step. A plot
>> showing this is in
>> http://folding.bmc.uu.se/images/Econserved-timestep.xvg or
>> http://folding.bmc.uu.se/images/Econserved-timestep.pdf
>>
>> MDP settings
>>    coulombtype                    = PME
>>    coulomb-modifier               = Potential-shift
>>    rcoulomb-switch                = 0
>>    rcoulomb                       = 1.1
>>    epsilon-r                      = 1
>>    epsilon-rf                     = inf
>>    vdw-type                       = PME
>>    vdw-modifier                   = Potential-shift
>>    rvdw-switch                    = 0
>>    rvdw                           = 1.1
>>    tcoupl                         = Nose-Hoover
>>    nsttcouple                     = 10
>>    nh-chain-length                = 1
>>    pcoupl                         = No
>>    ref-t:      298.15
>>    tau-t:         0.5
>>
>> Any clues whether we are doing something wrong? Or is there a bug?
>>
>> Cheers,
>


-- 
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205.
spoel at xray.bmc.uu.se    http://folding.bmc.uu.se