# The [[simulations]] section¶

The way to propagate the system is defined in the [[simulations]] section of the input file. This section always contains at least two keys: nsteps specify the number of steps in the simulation, and the simulations.propagator table specify which propagator to use.

Here is an example of NPT molecular dynamics:

[[simulations]]
nsteps = 1_000_000

[simulations.propagator]
type = "MolecularDynamics"
timestep = "1 fs"
integrator = {type = "BerendsenBarostat", pressure = "100 bar", timestep = 1000}
thermostat = {type = "Berendsen", temperature = "400 K", timestep = 100}


Three propagators are currently implemented: