npt_langevin_isotropic_init¶

torch_sim.integrators.npt.npt_langevin_isotropic_init(state, model, *, kT, dt, alpha=None, cell_alpha=None, b_tau=None, **_kwargs)[source]¶

Initialize an NPT Langevin state using logarithmic strain coordinate.

The strain coordinate ε = (1/d)·ln(V/V₀) provides well-scaled dynamics where the conjugate force F_ε = d·V·(P_avg - P_ext) is in energy units.

Parameters:

state (SimState) – Initial SimState
model (ModelInterface) – Model that computes energy, forces, stress
kT (float | Tensor) – Target temperature in energy units
dt (float | Tensor) – Integration timestep
alpha (float | Tensor | None) – Particle friction coefficient. Defaults to 1/(5·dt).
cell_alpha (float | Tensor | None) – Cell friction coefficient. Defaults to 1/(30·dt).
b_tau (float | Tensor | None) – Barostat time constant. Defaults to 300·dt.
_kwargs (Any)

Returns:

Initialized state with ε = 0

Return type:

NPTLangevinIsotropicState