Structure generation

matscipy-quench

This script carries out a liquid quench procedure. The structure is equilibrated at temperature T1, followed by an exponential quench to temperature T2. The script uses a Langevin thermostat for equilibration and quench.

matscipy-quench takes no command line parameters but expects a params.py file to be present in the current directory. An example params.py for liquid quench of an amorphous Carbon structure could look like this:

from ase.units import fs, kB
from atomistica import Tersoff, TersoffScr

stoichiometry = '4096C'
densities = [3.5, 3.3, 2.3, 2.5, 2.7, 2.9, 3.1, 2.0]  # Densites in g/cm^3

dt1 = 0.2*fs  # Time step for equilibration
dt2 = 0.2*fs  # Time step for quench
tau1 = 5e3*fs # Relaxation time constant for equilibration
tau2 = 0.5e3*fs # Relaxation time constant for quench
T1 = 10000*kB  # Equilibration temperature
T2 = 300*kB  # Quench down to this temperature
teq = 50e3*fs  # Equlibrate initial structure at T1 for this duration
tqu = 20e3*fs  # Total time of quench

quick_calc = Tersoff()
calc = TersoffScr()

The initial structure is just random positioning of the atoms. The calculator quick_calc is used for an initial optimization of the structure and can differ from the actual calculator. In the above example, a computationally less expensive potential is used for this initial equilibration. Equilibration at T1 and quench to T2 is then carried out with calc.