[gmx-users] Maximun time-step recommended in the grompp part for each system

[Mario Fernández Pendás]

Dear all,

Taking look at the check_bonds_timestep() function in src/kernel/grompp.c
used for checking the time-step used for the integration of the equations
of motion a few questions come to me:

- In the comments of the function it is said that "The stability limit of
leap-frog or velocity verlet is 4.44 steps per oscillational period". Does
anyone know how this exact number is obtained?

- I see that, inside of the function, there are two "limits": 5 and 10.
They are used for establishing a relation between the estimated oscillation
period of the bond between two atoms of the system in use and the time-step
used for integrating the equations of motion and giving a warning message
in case of using a non suitable time-step. I assume, looking at the
literature, that this limits are taking from the following paper by Mazur:
http://www.sciencedirect.com/science/article/pii/S0021999197957405
Am I right?

I have also found an issue in redmine for the function
check_bonds_timestep() reporting that it only reports the first suspicious
bond. I think this does not affect my questions.

Thank you very much.

Best regards,
Mario