dpd.hpp File Reference

Routines to use DPD as thermostat or pair force [42]. More...

#include <config/config.hpp>
#include "BoxGeometry.hpp"
#include "Particle.hpp"
#include "nonbonded_interactions/nonbonded_interaction_data.hpp"
#include "system/System.hpp"
#include "thermostat.hpp"
#include <utils/Vector.hpp>
#include <cmath>

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Namespaces
namespace	boost
namespace	boost::mpi

Functions
Utils::Vector3d	dpd_pair_force (DPDParameters const &params, Utils::Vector3d const &v, double dist, Utils::Vector3d const &noise)
Utils::Vector3d	dpd_pair_force (Utils::Vector3d const &p1_position, Utils::Vector3d const &p1_velocity, int p1_id, Utils::Vector3d const &p2_position, Utils::Vector3d const &p2_velocity, int p2_id, DPDThermostat const &dpd, BoxGeometry const &box_geo, IA_parameters const &ia_params, Utils::Vector3d const &d, double dist, double dist2)
Utils::Vector9d	dpd_pressure (System::System &system, boost::mpi::communicator const &comm)
	Pressure tensor contribution of the DPD interaction.
Utils::Vector3d	dpd_noise (DPDThermostat const &dpd, int pid1, int pid2)
	Return a random uniform 3D vector with the Philox thermostat.

Detailed Description

Routines to use DPD as thermostat or pair force [42].

Implementation in dpd.cpp.

Definition in file dpd.hpp.

Function Documentation

dpd_noise()

Utils::Vector3d dpd_noise	(	DPDThermostat const &	dpd,
		int	pid1,
		int	pid2
	)

Return a random uniform 3D vector with the Philox thermostat.

Random numbers depend on

1. dpd_rng_counter (initialized by seed) which is increased on integration
2. Salt (decorrelates different counters)
3. Two particle IDs (order-independent, decorrelates particles, gets rid of seed-per-node)

Definition at line 54 of file dpd.cpp.

References BaseThermostat::rng_counter(), BaseThermostat::rng_seed(), and stream.

Referenced by dpd_pair_force(), dpd_pressure_local(), and PressureKernel::operator()().

dpd_pair_force() [1/2]

Utils::Vector3d dpd_pair_force ( DPDParameters const &  params, Utils::Vector3d const &  v, double  dist, Utils::Vector3d const &  noise  )

inline

Definition at line 49 of file dpd.hpp.

References DPDParameters::cutoff, DPDParameters::gamma, DPDParameters::k, DPDParameters::pref, stream, and DPDParameters::wf.

dpd_pair_force() [2/2]

Utils::Vector3d dpd_pair_force	(	Utils::Vector3d const &	p1_position,
		Utils::Vector3d const &	p1_velocity,
		int	p1_id,
		Utils::Vector3d const &	p2_position,
		Utils::Vector3d const &	p2_velocity,
		int	p2_id,
		DPDThermostat const &	dpd,
		BoxGeometry const &	box_geo,
		IA_parameters const &	ia_params,
		Utils::Vector3d const &	d,
		double	dist,
		double	dist2
	)

Definition at line 75 of file dpd.cpp.

References dpd_noise(), dpd_pair_force(), P, stream, and BoxGeometry::velocity_difference().

Referenced by dpd_pair_force(), dpd_pressure_local(), Constraints::ShapeBasedConstraint::force(), ForcesKernel::operator()(), and PressureKernel::operator()().

dpd_pressure()

Utils::Vector9d dpd_pressure	(	System::System &	system,
		boost::mpi::communicator const &	comm
	)

Pressure tensor contribution of the DPD interaction.

This calculates the total contribution of the DPD interaction to the pressure tensor, i.e. the dissipative and random (noise) forces. It's calculated as the sum over all pair virials as

\[ P^{\nu\mu} = V^{-1}\sum_i \sum_{j < i} r_{i,j}^{\nu} F_{i,j}^{\mu} \]

where \(F_{i,j}\) is the DPD force (dissipative plus noise) exerted by particle j on particle i, \(r_{i,j}\) is their distance vector and \(V\) is the box volume.

Returns

Pressure tensor contribution.

Definition at line 154 of file dpd.cpp.

References dpd_pressure_local(), Utils::flatten(), and stream.

Referenced by ScriptInterface::Analysis::Analysis::do_call_method(), and Observables::DPDPressure::operator()().