[lammps-users] a question about respa

Hi, ALL

I used respa in the MD simulation like this,

Hi, ALL
I used respa in the MD simulation like this,
-------------------------------------------------------
timestep 1.0
run_style respa 2 2 pair 1 kspace 2
-------------------------------------------------------
How does the respa determine the inner level and the outer level ?

what "inner" and "outer" level?

you have requested two levels and
placed pair at level 1 and kspace at level 2
and since you give a factor of 2 between
level 1 and 2 you'll be doing pair (and implicitly
bond, angle, dihedral, improper) interactions
every step and kspace only every other step.

And, it doesn't apply to any minimization jobs, right ?

correct. minimization is not MD.

axel.

Hi, Alex

Thanks for your comment. I misunderstood the meaning of different levels by imagining that the whole system is divided into N parts and each part refers to one
level ( the part with the fastest motion, like O-H vibration, is the innermost, the part
with the slowest motion, is the outermost) .

In my case, the pair is evaluated every 0.5 fs and the kspace is evaluated every 1 fs.
Right ?

Regards,
Guozhen

Hi, Alex
Thanks for your comment. I misunderstood the meaning of different levels
by imagining that the whole system is divided into N parts and each part
refers to one
level ( the part with the fastest motion, like O-H vibration, is the
innermost, the part
with the slowest motion, is the outermost) .

you can have the bonded interaction handled separately as well.
the run_style command gives you the freedom (and responsibility)
to decide what to run how often.

In my case, the pair is evaluated every 0\.5 fs and the kspace is

evaluated every 1 fs.
Right ?

provided you have a 0.5fs time step, yes.

axel.