[gmx-users] PRESS-XX, PRESS-YY, PRESS-ZZ in .edr file

[Justin Lemkul]

On 8/5/19 10:55 AM, Anh Vo wrote:
> Dear Dr. Spoel,
>
> I understand that pressure here is the stress tensor with 6 components
> (PRESS-XX, PRESS-YY, PRESS-ZZ, PRESS-XY, PRESS-YZ, PRESS-XZ in 6
> dimensions), but I'm not sure if it is the per-atom stress tensor (averaged
> for all atoms), or the stress of the whole system?
> And for the PRESSURE, does it represent the pressure on the whole
> simulation system?

All pressure terms are for the whole system.

-Justin

> Thank you very much for sharing your time.
>
>> Hi all,
>>
>> I have searched online and GROMACS documentation for this question but I
>> haven't found any clear definition yet. Please help me to clarify it.
>>
>> In the output .edr file, there are PRESS-XX, PRESS-YY and PRESS-ZZ
> options.
>> What do they represent? Are they principal pressures (stresses) averaged
> for
>> all atoms during the simulation?
>> What is the difference between those options and PRESSURE option?
>>
>> Thank you very much.
>>
>> Best,
>> Anh Vo
>>
> THe pressure is a tensor, see manual.
>

-- 
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Justin A. Lemkul, Ph.D.
Assistant Professor
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