[Input: recipes/moleculardynamics/plumed2/]

Metadynamics is a class of methods that are used to estimate free energy (and other state functions) of a system in cases where normal ergodic sampling is difficult due to the system’s energy landscape.

PLUMED2 is a molecular dynamics biasing and analysis package that has been interfaced with DFTB+ to give metadynamics and free energy sampling functionality. It can select a wide range of collective variables to sample systems, such as the distance between pairs of atoms or specified torsion angles.

To use PLUMED2, DFTB+ must be compiled with support for this enabled (and a compiled version of the plumed library available, see the plumed website). Set the Plumed tag in the Driver input block to Yes with VerlocityVerlet selected as the geometry driver. A plumed.dat input file must also be present in the run directory

Driver = VelocityVerlet{
TimeStep [fs] = 1.0

Plumed = Yes

Thermostat = NoseHoover {
Temperature [Kelvin] = 400
CouplingStrength [cm^-1] = 3050
}
.
.
.
}


The plumed.dat file contains information to be read by the PLUMED2 code that will allow it to either bias or analyse the molecular dynamics on the fly.:

DISTANCE ATOMS=4,9 LABEL=d1
DISTANCE ATOMS=5,9 LABEL=d2