MTTK¶

class hoomd.md.methods.thermostats.MTTK(kT, tau)¶

Bases: Thermostat

The Nosé-Hoover thermostat.

Controls the system temperature using velocity rescaling with the Nosé-Hoover thermostat.

Parameters:

kT (hoomd.variant.variant_like) – Temperature set point for the thermostat $[\mathrm{energy}]$ .
tau (float) – Coupling constant for the thermostat $[\mathrm{time}]$

The translational thermostat has a momentum $\xi$ and position $\eta$ . The rotational thermostat has momentum $\xi_{\mathrm{rot}}$ and position $\eta_\mathrm{rot}$ . Access these quantities using translational_dof and rotational_dof.

Note

The coupling constant tau should be set within a reasonable range to avoid abrupt fluctuations in the kinetic temperature and to avoid long time to equilibration. The recommended value for most systems is $\tau = 100 \delta t$ .

Examples:

mttk = hoomd.md.methods.thermostats.MTTK(
    kT=1.5,
    tau=simulation.operations.integrator.dt * 100,
)
simulation.operations.integrator.methods[0].thermostat = mttk

kT¶

Temperature set point for the thermostat $[\mathrm{energy}]$ .

Examples:

mttk.kT = 1.0

mttk.kT = hoomd.variant.Ramp(A=1.0, B=2.0, t_start=0, t_ramp=1_000_000)

Type:: hoomd.variant.variant_like

tau¶

Coupling constant for the thermostat $[\mathrm{time}]$

Example:

mttk.tau = 0.2

Type:: float

translational_dof¶

Additional degrees of freedom for the translational thermostat ( $\xi$ , $\eta$ )

Save and restore the thermostat degrees of freedom when continuing simulations:

Examples:

Save before exiting:

numpy.save(
    file=path / "translational_dof.npy",
    arr=mttk.translational_dof,
)

Load when continuing:

mttk = hoomd.md.methods.thermostats.MTTK(
    kT=1.5,
    tau=simulation.operations.integrator.dt * 100,
)
simulation.operations.integrator.methods[0].thermostat = mttk

mttk.translational_dof = numpy.load(file=path / "translational_dof.npy")

Type:: tuple[float, float]

rotational_dof¶

Additional degrees of freedom for the rotational thermostat ( $\xi_\mathrm{rot}$ , $\eta_\mathrm{rot}$ )

Save and restore the thermostat degrees of freedom when continuing simulations:

Examples:

Save before exiting:

numpy.save(
    file=path / "rotational_dof.npy",
    arr=mttk.rotational_dof,
)

Load when continuing:

mttk = hoomd.md.methods.thermostats.MTTK(
    kT=1.5,
    tau=simulation.operations.integrator.dt * 100,
)
simulation.operations.integrator.methods[0].thermostat = mttk

mttk.rotational_dof = numpy.load(file=path / "rotational_dof.npy")

Type:: tuple[float, float]

property energy¶

Energy the thermostat contributes to the Hamiltonian $[\mathrm{energy}]$ .

Example:

logger.add(obj=mttk, quantities=['energy'])

(Loggable: category=”scalar”)

thermalize_dof()¶

Set the thermostat momenta to random values.

thermalize_dof sets a random value for the momentum $\xi$ . When hoomd.md.Integrator.integrate_rotational_dof is True, it also sets a random value for the rotational thermostat momentum $\xi_{\mathrm{rot}}$ . Call thermalize_dof to set a new random state for the thermostat.

Example

mttk.thermalize_dof()

Important

You must call Simulation.run before thermalize_dof.