LangevinMiddleIntegrator

class LangevinMiddleIntegrator : public OpenMM::Integrator

This is an Integrator which simulates a System using Langevin dynamics, with the LFMiddle discretization (J. Phys. Chem. A 2019, 123, 28, 6056-6079). This method tend to produce more accurate configurational sampling than other discretizations, such as the one used in LangevinIntegrator.

The algorithm is closely related to the BAOAB discretization (Proc. R. Soc. A. 472: 20160138). Both methods produce identical trajectories, but LFMiddle returns half step (leapfrog) velocities, while BAOAB returns on-step velocities. The former provide a much more accurate sampling of the thermal ensemble.

Public Functions

LangevinMiddleIntegrator(double temperature, double frictionCoeff, double stepSize)

Create a LangevinMiddleIntegrator.

Parameters

  • temperature – the temperature of the heat bath (in Kelvin)

  • frictionCoeff – the friction coefficient which couples the system to the heat bath (in inverse picoseconds)

  • stepSize – the step size with which to integrate the system (in picoseconds)

inline double getTemperature() const

Get the temperature of the heat bath (in Kelvin).

Returns

the temperature of the heat bath, measured in Kelvin

void setTemperature(double temp)

Set the temperature of the heat bath (in Kelvin).

Parameters

temp – the temperature of the heat bath, measured in Kelvin

inline double getFriction() const

Get the friction coefficient which determines how strongly the system is coupled to the heat bath (in inverse ps).

Returns

the friction coefficient, measured in 1/ps

void setFriction(double coeff)

Set the friction coefficient which determines how strongly the system is coupled to the heat bath (in inverse ps).

Parameters

coeff – the friction coefficient, measured in 1/ps

inline int getRandomNumberSeed() const

Get the random number seed. See setRandomNumberSeed() for details.

inline void setRandomNumberSeed(int seed)

Set the random number seed. The precise meaning of this parameter is undefined, and is left up to each Platform to interpret in an appropriate way. It is guaranteed that if two simulations are run with different random number seeds, the sequence of random forces will be different. On the other hand, no guarantees are made about the behavior of simulations that use the same seed. In particular, Platforms are permitted to use non-deterministic algorithms which produce different results on successive runs, even if those runs were initialized identically.

If seed is set to 0 (which is the default value assigned), a unique seed is chosen when a Context is created from this Integrator. This is done to ensure that each Context receives unique random seeds without you needing to set them explicitly.

virtual void step(int steps)

Advance a simulation through time by taking a series of time steps.

Parameters

steps – the number of time steps to take